After getting about two or three threads, sometimes on the very first page it seems like about the question:

"What can I do about my MPG?"

With fuel prices over record breaking highs, we all are asking this same question. So I'd like to summarize for everyone some of the great ways that you can help to max out your MPG's.

1. Reduce cruising speed - running diesel engines at higher RPM's gobbles up more fuel than gasoline engines do.

2. Reduce idling. This too gobbles up more fuel than a gasoline engine will.

3. Fast accelleration - You have a lot of torque available at lower RPM's than a gasoline engine, but that torque comes from fuel. Getting hard into the go pedal will reduce your MPG's.

4. Rear gearing - not much most of us can do about this. 4.10 rear is great for get up and go and towing, but reduces fuel milage. 3.73 is better, 3.42 is really good for fuel, but reduces the capacity of towing capabilities.

5. Clean air filter

6. Injectors - injectors "wear" - or lose some of there optimium settings and spray abilities over time. If injectors are going out of spec, you *could* be losing some engine efficiency.

7. Tire pressure - full spec on your pressure helps.



A note on fuel milage measurement. If you don't top off your tank to the fullest, your numbers will tend to drift one way or another. It's best to be as scientific about things as possible when making your measurements. Also, don't take one tank as "in stone" measurements. Average them over the next few tanks.


This thread is open for everyone to contribute to.

I gained 1 mpg by gutting kitty, mandrel bent crossover and downpipe and 4 inch out from empty cat back. Free flowing exhaust helps a little IMO.

1. Be sure your thermostat is the correct one to keep coolant temp at least 180 - 190degf.

2. Reduce weight by removing any unnecessary weight in the truck that you don't need.

3. If driving an automatic try to get to up to speed where TCC is locked and in high gear fairly quickly (without dogging it).

4. Turn off A/c when not needed.

5. Use synthetic fluids in the engine, tranny and differential.

6. Don't drive with the tailgate down. This has proven to decrease mileage. A tonneau cover increases mileage on highway, but probably decreases mileage if most of your driving is in town or at slower speeds due to the estra weight.

7. Don't use tires with aggressive tread (ie mudgrips) unless you need them. Highway tires get better fuel mileage.

8. When pulling a trailer, try to keep load as low as possible to reduce drag.

About 18 months ago I asked members about their best fuel saving tips. There were were about 30 great tips that hold true today:

http://www.dieselplace.com/forum/showthread.php?t=97786

I know this is a given, but check for fuel leaks. I had one and after I fixed it, my mileage jumped. Check under the fuel filter for any small leak, if there is fuel there, fix it, no sense in putting $5 gallon diesel on the pavement.

I heard a Tornado, K&N, and some acetone in the tank will double your fuel mileage.



If you recalibrate the speedo 2:1...

I installed the factory replacement style K&N air filter in my Dmax and I picked up 1.5 MPG. The acetone does work we tryed it our PowerJoke (7.3) and it picked up 2 MPG (over 10% increse) (fuel lubertcant recomended). The tornado on the other hand is a joke anything in the air stream to "change direction" of the air is only a restriction like a dirty air filter. We have tested this at my college (it reduced fule economy).

Quote from the linked thread.

Please note folks that acetone is NOT a recommended additive to your fuel system, damage will occur to it's components!

I think the title of the thread should be "Fuel Saving", not "How to get better MPG." No matter what MPG you get, if you have 20% more fuel in your tank at the end of the week you've saved 20%.

Here are some ideas for saving fuel that can lower your GPM (gallons per month). I've guestimated each one on a 10-point scale with 1 being the least savings and 10 the most savings. Don't use M&S tires all year round. (+7)
Don't carry around unnecessary weight (+2)
Never use your brakes. Keep your truck moving as much as possible. (Notice how much you are pushed forward when you brake and then imagine how much fuel it will take to press you back in the seat that same amount. That's exactly how much fuel you will need to re-accelerate your truck.) (+6)
Use your GPS to plot the most efficient order to make multiple stops. This can save huge amounts of distance and fuel. (+7)
Use your GPS to plot the shortest route. Even half a mile saved in a 5 mile trip is a 10% savings! (+7)
Don't keep your tank full - keep it half full. Fifty gallons of fuel weighs 400 lbs. Be careful - because you have to visit gas stations more often see next point. (+1)
Don't drive TO a gas station - stop off at one you are driving past. If you make a special trip to a station 5 miles away the extra fuel you use is the equivalent of paying an extra 5-7 cents per gallon, depending on your mileage! (+2)
Use the appropriate vehicle. If you don't need the truck don't take it. If you have a car always use the most efficient vehicle for the job. You don't need a 6,000 lb truck to pick up a loaf of bread - you do need it for a load of gravel.(+5)

take a look at those auxillary units for overdrive and underdrive i've heard alot about people saving fuel with those but i've personally never tried them another thing i've seen is the kits that they are selling that make hydrogen out of water they advertise 30 to 70 % increase in fuel mileage but i don't know i've never tried them.

acetone?cetane to increase mileage mabey.I just took my N/A for a trip and got 28 MPG(canadian gallon)or 23.5 mpg(US).With a slight tail wind.17 city driving.TDCO at -.70 engine at 1750 RPM doing 104 KM per hour.With my other truck which is a turbo if I keep it under 100 kph it gets 24 mpg(can)As soon as I go over that mileage suffers. Check to make sure there is no drag in the braking system,e-brake ect.Have not tried it but some say highway driving with the tailgate down also helps mileage.

Actually, driving with the tailgate down decreases mileage.

Driving with the tailgate up causes negative pressure in the bed, thus creating a venturi effect in the bed of the truck, pushing the air stream that is coming over the cab straight past, rather than down.

Driving with the tailgate down does not allow the venturi effect to be created, so the air stream comes over the cab and down into the bed, applying positive pressure to the bed.

It doesn't effect is much, but it is a myth that driving with the bed down increases mileage.

The Mythbusters did a pretty good demonstration of this in a wind tunnel.

X2 on driving with the tailgate down. You can visit mythbusters website - they actually did two different test on this myth....tailgate up=better fuel economy. But I think they tried all sorts of configurations, tail gate down, up and removed and even tried one of those air gates and if I remember correctly the airgate did get better mileage than any other configs.

I've been testing mpg over the last ten tanks or so. Basically driving back and forth to work 32 miles round trip(20 highway and 12 city) driving 65 mph/2000 rpms = 17.6 mpg over 30 gals fuel, driving 62/3 mph/1800 rpms = 18.4 and driving 60 mph at about 1700-1750 rpms been gettin 18.6 - 19 mpg. Also, I don't accelerate hard and I shift around 2200 rpms.

http://www.dieselplace.com/forum/showthread.php?t=240247
Looks like electric fans have given me +1 city and +2 combind city and high way driving.

I also took off the clutch fan on my truck and saw a major increase in city driving.Also the truck is quieter.my truck is a N/A.The temp does not go over 200f driving around.80 ambient.I have not installed my electric fans yet.

Odlaw, IIRC, the air-gate on the bed resulted in the worst mileage of any test they did.

"I have not installed my electric fans yet".
You're brave. I took my truck for few short trips to see 1 if the engine would freak out if it didn't have that load at idle (some vehicles do), 2 see how much quieter the engine is, 3 see if there is any more power on tap form 0mph.
I was all ways back home before it reached full temp.
Things I noticed right away with no fan, 1 the engine cranked faster, 2 it was quieter, 3 more power when my foot first hits the "gas", 4 its about a 100x safer to be working around the engine when its running, 5 there is more room to work on the engine.
And also gas milage went up.
In the city it looks like I got a +1mpg boost that is about a 6% boost to fuel economy. I will take that any day of the week.
In the mixed high way/city test I gained about +2mpg, that is about a 10% boost to fuel economy.
I belive straight high way driving will net me +3 mpg, that would be about a 12% boost to fuel economy. Mmmmm.

This mod is economical, It will pay for its self. I have $80 in those 3 fans and maybe a nother $20 in relays and wires and junk. So buy about my 10th fill up I should have saved about $100 in fuel if my economy is just boosed 10%.
Its more cost effective then paying 100's of dollars for an exhaust that gives you +1mpg.

My next mod will be to replace the old stock looking mufflers with thrush turbo mufflers, delete about 6 feet of pipe (I have duel pipes, and will get rid of at least 3ft off each side) and dump forward of the rear axel.
If I get +1mpg off $60 worth of mufflers and some pipe I will be very happy.

Yea.no fans yet.The only thing I am worried about is the tranny temp.I am installing a temp gauge tommorow.Turning the A/C on may cause some issues but I havent tried it yet either.With 80 degree ambient engine has not gone over 205 yet.I have let it idle,driven in city traffic ect.No problems yet.I noticed a very signifigant increase in mileage though.

A/C will hardly work with zero airflow across it at idle. In fact the heat radiating off of the radiator into the condenser since sans fan... you'll be gittin' toasty when the high pressure switch pops.

Will be installing electric fans sometime soon.I am thinking of wiring the fans into the A/C circuit.as soon as the a/c is turned on it will bring the fans on.

Will be installing electric fans sometime soon.I am thinking of wiring the fans into the A/C circuit.as soon as the a/c is turned on it will bring the fans on.
I am doing that with the 12'' pusher fan I installed but have not wired yet.
I was going to take power off the compressor clutch use it to power a relay to the fan and it will be good to go. And also a manual switch, for back up or extra cooling when/if needed.

One other consideration for folks too is the tire size. Some folks say "I just up sized my tires and now I have better fuel mileage" - of course now, if your speedometer is not reading correctly, then the science is slighly off a bit as to real true mileage...

I have to add +3% to my odometer miles because of my tire size change.

Bigger tires will show less on odometer.smaller tires will show more on odometer.

Other efficiency upgrades that I know of:

Alloy Rims: they look cool, and they weigh less, less weight=better mileage

clean vehicle: less drag at speed (this probably only matters above 60 or so)
air dam: supposedly runs cooler (lower air psi under vehicle, air flows better out of engine comp.) and the air is routed to the sides, basically cuts the wind better for better mileage.

Magnetic fuel particle aligners on your high pressure lines help pre-orientate fuel molecules to better atomize in the chamber too ;)

OK, here's a serious one, if your 6.5 smokes black, lightly, if its heavy you just need to get it fixed, but if its light, especially under light accel, then you can drop your calibration resistor by a couple #'s to recompensate fuel delivery to eliminate the smoke. And because black smoke is wasted fuel this means less waste/better economy.

Additionally, if fuel economy is #1 concern, then put a #1 resistor in. Conversely, if you want power and money to buy fuel is no object, then you want a #9.

Also, just remembered this, if you want on the fly fuel/air compensation without chaging anything on the pump, search for old posts on pot(entiometer) on MAP sensor. This allows on the fly "tuning" of boost pressure to eliminate smoke/tweak performance.

Magnetic fuel particle aligners on your high pressure lines help pre-orientate fuel molecules to better atomize in the chamber too ;)

OK, here's a serious one, if your 6.5 smokes black, lightly, if its heavy you just need to get it fixed, but if its light, especially under light accel, then you can drop your calibration resistor by a couple #'s to recompensate fuel delivery to eliminate the smoke. And because black smoke is wasted fuel this means less waste/better economy.

Additionally, if fuel economy is #1 concern, then put a #1 resistor in. Conversely, if you want power and money to buy fuel is no object, then you want a #9.


the difference between a #1 to a #9 is very slight. barely noticeable. another way to get rid of the black smoke is to up the boost(up to 15 psi max sustained with an intercooler). i'm running 11-12 psi boost with the heat computer which changes the fuel curves. under WOT i see a cloud of smoke until the turbo spools up then the smokes gone.

I did a run today,, decieded to figure out the mileage,,,So my tank has had in the last 3 fill ups,, 10.6 gal of #2 and then filled with My Home Brewed Bio, (34Gallon Tank) driven for 312 miles, and filled up again today with my Brew. I then drove, 137 miles @ about 65MPH on the Highway for 65% of the trip and 55MPH for the rest of the trip,, stopped to top off the tank with #2 and it was 10.5 gallons. So my truck in Sig is getting 13.04 MPG on what I would call about B80~B90mix. 4x4 with 4:10's =)
@ about$1.10 per gallon,, I'm not as concerned with MPG as I am when filling up @4.69 to the tune of about $165!!!

This mod is economical, It will pay for its self. I have $80 in those 3 fans and maybe a nother $20 in relays and wires and junk. So buy about my 10th fill up I should have saved about $100 in fuel if my economy is just boosed 10%.
Its more cost effective then paying 100's of dollars for an exhaust that gives you +1mpg.

My next mod will be to replace the old stock looking mufflers with thrush turbo mufflers, delete about 6 feet of pipe (I have duel pipes, and will get rid of at least 3ft off each side) and dump forward of the rear axel.
If I get +1mpg off $60 worth of mufflers and some pipe I will be very happy.[/quote]
for those running with electric fans summit has a temp gage that can be set at any temp from 100-300 to trip a relay.
as for the muffler try strait pipe no back pressure. i have seen mufflers that are louder than just pipe on a turbo.

I also took off the clutch fan on my truck and saw a major increase in city driving.Also the truck is quieter.my truck is a N/A.The temp does not go over 200f driving around.80 ambient.I have not installed my electric fans yet.

Do you know exactly how much you picked up?



My next mod will be to replace the old stock looking mufflers with thrush turbo mufflers, delete about 6 feet of pipe (I have duel pipes, and will get rid of at least 3ft off each side) and dump forward of the rear axel.
If I get +1mpg off $60 worth of mufflers and some pipe I will be very happy.

I completely freed up my exhaust and gained nothing.

My van is a bastard child, I've put on headers, free flowing exhaust, turbo lower intake removing the egr intake, opened up the intake, ram air, different IP and my mileage is always 17-18mpg, :confused:Censored

It sounds like you have lots of power and maybe to much gear.
So does it have 3.08's or 3.73's?
Being in a G van body could have some thing to do with it that is for sure.

It sounds like you have lots of power and maybe to much gear.
So does it have 3.08's or 3.73's?
Being in a G van body could have some thing to do with it that is for sure.


See sig, :D

ok so it looks like you swaped in 3.73's.
Yea, those hurt fuel milage.
After I finish the exhaust I will be getting about all the power to be had from an N/A 6.2L.
Just about the only thing I haven't done is added headers.
A turbo would be nice, then I would have the power to swap in 2.73 gears.

ok so it looks like you swaped in 3.73's.
Yea, those hurt fuel milage.
After I finish the exhaust I will be getting about all the power to be had from an N/A 6.2L.
Just about the only thing I haven't done is added headers.
A turbo would be nice, then I would have the power to swap in 2.73 gears.

No, I have 3.08's, I have YET to install 3.73's, :o:

If your towing, lower gears, even with a turbo still make the engine work harder and produce more heat. If mean towing with 2.73 gears, your powertrain won't last long. I could probably get away with 3.08's and a turbo if the van didn't have the aerodynamics of a brick.

Are you going to use it as a towing machine?
how hard is it to modify hummer headers to fit in place of the stock manifolds in a truck body?

Are you going to use it as a towing machine?
how hard is it to modify hummer headers to fit in place of the stock manifolds in a truck body?

I have an enclosed trailer to tow and I now have a 22 ft camping trailer. But mostly, its a DD or towing a small trailer. I can't use it really to go to the states as I have to wind out 3rd gear and can only do 50-60 mph on average, :(

I have a thread in the 6.2 section, search my name and headers, not sure on trucks how hard to modify.

While I was home on leave I got on average 16.5MPG. That is with a mis of city / hwy driving. I did not take it easy, and I did not dog on it.

16.5MPG?
You plan on fixing that?

16.5mpg sounds good to me!
But if it needs fixing tell me what you think I need to do!

How about a Scanguage II or equivelent, it shows realtime mileage so you can change your driving habits on the fly

How about a Scanguage II or equivelent, it shows realtime mileage so you can change your driving habits on the fly

Actually the ScanGauge 2 is so "real time" that you almost can not hold it steady to maintain a good mileage number. It needs about a 15 second average in order to be able to use it like that. Even when my cruise control is on, the MPG number changes when the wind gusts change and with the slightest change in grade. You have to stare at it for a while to get an "eye-ball-average". Of course you can look at the average mileage for the tank so far. All of this is only valid if you've got it calibrated and I'm still working on that on my third tank.

It's a good instrument, don't get me wrong. It's still being improved and I'd still buy it. Why, just tonight on the way home while fiddling with my new TorqLoc I managed to piss off the PCM and brought up the SES light. I then proceeded to call up the code on the ScanGauge. wrote it down, cleared it and got the transmission out of limp-mode, all while running along at freeway speed. Sweet.

Mike

my truck is a 1993, I can not find a scanguage II that will work with my truck. Also my truck is a mechanical injected truck!
Thanks for the advice! I wish I could have a scan guage.

my truck is a 1993, I can not find a scanguage II that will work with my truck. Also my truck is a mechanical injected truck!
Thanks for the advice! I wish I could have a scan guage.

your lucky not to have a pmd

I've got a 94, 4 door long bed 2WD dually with 4.10 gears from the factory, stock tire size, etc. I'll never tow more than 5-7k lbs with it so I'm considering swapping the gear ratio. It already has straight exhaust, a K&N air filter, I opened up the factory air box with a 3" hole saw so it can breath better, and made a TM for it. So far it seems to be getting no better than 15mpg. Previous owner claimed he got 23mpg with it, but I can't see that. What's your opinion on swapping gears? I have quite a bit of diff experience and can swap them myself so it's simply a matter of buying gears. I'm afraid 3.73 wont be enough of a change for me, but I'm also scared that 3.42's will kill any towing ability even though I don't tow very often with it. Mostly just a daily driver but I'd like to cruise 70mph on the highway.

I've got a 94, 4 door long bed 2WD dually with 4.10 gears from the factory, stock tire size, etc. I'll never tow more than 5-7k lbs with it so I'm considering swapping the gear ratio. It already has straight exhaust, a K&N air filter, I opened up the factory air box with a 3" hole saw so it can breath better, and made a TM for it. So far it seems to be getting no better than 15mpg. Previous owner claimed he got 23mpg with it, but I can't see that. What's your opinion on swapping gears? I have quite a bit of diff experience and can swap them myself so it's simply a matter of buying gears. I'm afraid 3.73 wont be enough of a change for me, but I'm also scared that 3.42's will kill any towing ability even though I don't tow very often with it. Mostly just a daily driver but I'd like to cruise 70mph on the highway.

Currently it shows 2600rpm at 70mph. I've read were 1800rpm is optimum economy for the 6.5TD but that's only about 50mph for me. I did find my truck had the wrong alternator pulley on it and I've already swapped to the larger 62mm pulley. Before this correction I was showing 2800rpm at 70mph. I'm confident the tach is much more accurate now.

You can see huge gains by simply not burning the gas in the first place. I've been told that if you know you'll be idling for more than 30sec, kill it. The book I've listed below goes into painful detail about saving energy and how to do it (on a macro scale) but many of the ideas can be applied to daily use. Idling accounts for 17% of the automotive fuel used. The book can be downloaded for free.

www.oilendgame.com

I found that if i stayed out of Tim Horton's drive through I could increase my milage a lot, but I found myself falling asleep at the wheel;)

My life time average is about 17.6

I've kept track since day 1 since Im on one of those hypermiller forums

my truck is a 1993, I can not find a scanguage II that will work with my truck. Also my truck is a mechanical injected truck!
Thanks for the advice! I wish I could have a scan guage.


Cash, I also have a 93, and am a little unhappy that I can't chip it. Glad not to have to deal with the PMD and associated electronics though.
Rock on.:D

i see most people saying they get like 20-17mpg im wondering if there is something wrong with my 6.5 because im only getting like 14.5-15mpg and its been pretty constant i just cleaned out my air filter and that was pretty dirty but something just dont seem right

I've got a 94, 4 door long bed 2WD dually with 4.10 gears from the factory, stock tire size, etc. I'll never tow more than 5-7k lbs with it so I'm considering swapping the gear ratio. It already has straight exhaust, a K&N air filter, I opened up the factory air box with a 3" hole saw so it can breath better, and made a TM for it. So far it seems to be getting no better than 15mpg. Previous owner claimed he got 23mpg with it, but I can't see that. What's your opinion on swapping gears? I have quite a bit of diff experience and can swap them myself so it's simply a matter of buying gears. I'm afraid 3.73 wont be enough of a change for me, but I'm also scared that 3.42's will kill any towing ability even though I don't tow very often with it. Mostly just a daily driver but I'd like to cruise 70mph on the highway.
Correct me if Im wrong , but the lower numerical gear ratio's are not going to totally kill your towing capibilites. My Suburban has the 3.42's, I towed our car to the Smokies this past Memorial Day and had no problems. Total weight being towed was about 5000 lbs, EGT's never got over 850 degrees. Now when towing near max capacity I will totally agree stay away from very heavy loads. Unless of course you want to burn up something! :eek:
I have averaged close to 19-20 MPG since owning my truck.

I guess this is the place to chime in about fuel economy. We got our suburban from the wifes sister about 9 or 10 months ago. Sister in law told the wife about the fantastic mileage it gets but you know how everybody stretches the truth when it comes to mileage or fishing. For the last 9 months we've done little more than poke around town in it and several checks have shown that it's getting about 15 around town here which I was not too surprised with. This past holiday weekend we took our first road trip with it to see our son who lives 400 miles from here. We only fueled twice, one when we were ready to leave his place and come home, and again when we got back to the house. Both fillups showed the mpg to be just under 20, (18.7 and 19.6). That did surprise me, I was expecting worse. I don't know if this is average, good, or bad, but I am pretty happy that 1 gallon of liquid diesel fuel can push our 5,000 pound vehicle, me, moma, and all of momas things that she stuffs the car with when we go on a trip almost 20 miles down the highway at 70 miles per hour. I have no idea what the gear ratios are in it but I would say everything is stock. Is this pretty typical ?:rolleyes: It's a 95 1500 SLE 4x4 with 133k miles on it.

i see most people saying they get like 20-17mpg im wondering if there is something wrong with my 6.5 because im only getting like 14.5-15mpg and its been pretty constant...

Most folks don't give the details of their rigs to really compare mileage. Pickup vs. Suburban, manual vs. automatic, 2wd vs. 4wd, tire sizes, cruise speed, how many cold starts on a tank of fuel, etc, etc.

If I fill up when the engine is warm and make my standard weekly run up the I-5 freeway (Portland to Tacoma), empty, drive with the big trucks at 60 mph (max) with the cruise control on, maybe one or two cold starts on the fillup, I can get 17-1/2 mpg. If I drive it "normal" with a dozen cold starts on the tank, stop and go between home and the barn, 70-75 on the freeway, I'll get 14-1/2. You can see what I'm driving in my signature.

I'm a licensed gadget nut and I keep detailed records of my mileage vs. driving style. I just picked up a set of Goodyear Wrangler HT 235/85-16 tires and wheels from Craigslist so I can compare them with my new BFG Long Trail 265/75-16s; same diameter, about an inch narrower. I'm told by a friend who is many decades in the tire business with a lot of high performance experience (Nate Jones Tires, San Diego) that I'll see better mpg with the narrower tires. I should have some good numbers to compare by about next summer at the rate I drive my truck.:rolleyes:

It's a lot of little things that add up to better mileage. I just switched to Mobile 1 diesel oil and I see a slight improvement in the last two tanks. It'll take a dozen tanks to pay for the expensive oil and then it'll be time to change it again, but, this is all for fun anyway, right? ...

Mike

Update on mine. Around town as a daily driver I've seen 15-17mpg on average. We took a 600 mile trip (each way) to Chicago for Chrstmas last week. Set the cruise on 65mph for the entire trip and still no better than about 17mpg.

I've just picked up a 1996 3500 extended cab dually with a 6.5 turbo and only 68000 miles. I changed the oil and air filter, hitched it to a 24 foot enclosed trailer and hauled it from Chicago to Florida and back. I only got 10 mpg. Speed was 60 t0 70 mph and it seemed to do better above 65. Does that seem right or am I using too much fuel? I'd been told to expect 15 mpg towing. This is my first diesel tow rig, so I'm not sure what to expect. Any real world response would be appreciated. Do I need to fix the truck or reset my expectations?

You should expect the 17 1/2 mpg +/- without even trying. It's just the way it is.

Hot rod starts and a lot of full throttle will work against you.

Use the cruise control as much as possible.

My best economy is at 62.5 mph. I like to drive at 70, but hold back on that.

IMHO the small amount of time saved by going faster is not worth the extra cost for the fuel, and the driver fatigue caused by having to constantly negotiate traffic.

If you want to get there sooner, then leave early.

When I bought my truck the only rear end ratio available from the factory was 4.10. To get anything different one would have had to have it changed on their own at extra cost.

Other important factors are tires and pressure. I run a set of Michelin LT267/75R16 @ 65 to 70 psi. Great ride and tire life!

I have (I thought) gotten between 18 and 19 MPG with my truck
since I got it 5 years ago -mixed city/hwy.
Truck had 245/75/16s on it, speedo was off by 3 MPH - when it showed
60, actual speed was 57 - bought new tires recently, went to 265/75/16s,
and now my speedo is dead on - and my MPGs are 16.5 -17.5 :(
Still not bad, but not as good as I thought they were - oh well,
got 13.5 on a 700 mile trip, pulling my Jeep and trailer (about 6000 lbs)
probably wouldn't get that using the Tahoe

I've just picked up a 1996 3500 extended cab dually with a 6.5 turbo and only 68000 miles. I changed the oil and air filter, hitched it to a 24 foot enclosed trailer and hauled it from Chicago to Florida and back. I only got 10 mpg. Speed was 60 t0 70 mph and it seemed to do better above 65. Does that seem right or am I using too much fuel? I'd been told to expect 15 mpg towing. This is my first diesel tow rig, so I'm not sure what to expect. Any real world response would be appreciated. Do I need to fix the truck or reset my expectations?

That mileage is about dead on for that load, your pushing alot of air there. When my 92 was new pulling a 24' gooseneck cattle trailer on old school fuel I'd get around 11mpg, with the newer LSD it was always around 10mpg with fuel conditioner, I dont know how bad it would do with the newer ULSD since I dont tow very far/heavy with it any more.

The Dmax seems to do better towing, 11-11.5 or so with that trailer and 10.5-11 pulling a 32', I guess because its intercooled and does it so much easier. Empty you have to really baby it or the 6.5's will beat it on mpg's pretty easy, IIRC, I dont drive it empty very often though, it stays hooked to a trailer(keeps the miles off it that way;)).

Thanks. That was the honest answer that I was looking for. Since my previous post I've gotten 15mpg combined city/highway without a load by keeping the speed at 60-70 mph. I'd love to get a Gear Masters overdrive but that's a whole lot of money.

Well as of yesterday i was getting 14.5 in the city, which is not that bad for where I live (lots of stop and go). But i am going to stay off the pedal this tank and see what I get. Give me a few days though. 34+3 gallons takes a while to burn.

Ditto what plowboy said. Lotta air resistance and 4.10 gears.

My sub w/ 3.42's would repeatably run 21.2mpg empty at 65 and 19.6mpg at 70. It got 14.6mpg towing 9000lbs at 65-70, but it was tractor and such on an equipment trailer - not near the drag of an enclosed trailer.

My sub w/ 4.10's ran 17.1mpg at 70 on my most recent trip and I get about 13.5 to 14.5 daily driving. Haven't made a heavy tow run yet to comment.

Just make sure your lift pump is working good and you have clean air and lots of PSI in the tires...

Chaser

These responses have been a great help to me. Thank you all!

12-14 in the cities and 18-20 on the free-way 95 burb not bad

I used to get good mileage, 19 - 20 to work 6 miles away and back. 20 - 22.5 on the freeway at 65 - 70 pmh.
Then everything went to hell in a hand basket and I haven't been able to get it back.
I put on new remote PMD, new rear tires that are slightly taller 265/70/15 from 235/75/15 and it was Oct/Nov so winter fuel showed up in the pumps, plus the new Ultra low sulfur fuel that adds the problem, less BTUs. This week I discovered my Turbo wastegate solenoid is out... so wire the turbo shut until I get a new solenoid! :D
It runs great, maybe I should just leave it! :eek:
I hardly ever run over 1900 rpms. It used to be like clock work, 130 miles the fuel gauge would move off of full, 200 it would read 3/4 full, at 300 miles 1/2 a tank. Right now I have 184 miles on the current tank and it reads 5/8 full. But most of the mileage was before I FIXED the waste gate. Hoping a new solenoid will bring back the mileage.

Best thing you can do to reduce your fuel cost, is mix your pump diesel with 50 percent cooking grease, that you get for free from local resturants! My 6.5 runs great on it. Just becareful of your mixture in the winter.

Just went through first 3/4 tank on my 93 and just it 59k:). Almost all in town driving 17.5 mpg. Couldn't be happier, can't wait to see what I get on the interstate.:D

I've got a 96 k3500 I get 13 mpg on highway empty, 11 pulling my 18' boat. Bare bones stock truck 296k. don't think the injectors have ever been changed so i'm getting a set of marines. Hoping this will help a bit

no power either 30 mph up an 8% hill with the boat. Did a diy propane fumigation. works great! but no change in mpg. Need an egt before i try an big hills

Wife's 95. 23.6 ml/gal combined city/high way.

12 City 16 Hwy

Newbie poster - Looking for the right thread – this looks a good a place as any.

I drive my suburban mostly on weekends hither and thither and it seemed to get about 18 MPG country & city driving with AC running.

In may, I dragged a 6X12 U-haul (2K lbs empty) from the Miami Area to San Francisco Area and back tallying roughly 6600 miles.
Just before leaving, I installed a #9 resister, added (homemade) propane injection and installed the trio of gauges.

Propane usage is approximately 1 gallon propane to 10 gallons of Diesel.
The empty duel axle trailer pulled hard and yet I was able to maintain 20+ MPG on diesel or about 18+ MPG when the propane usage is figured in. On the return trip a full load of household goods, I maintained about 17+ MPG on both fuels.
At one point in the trip I ran out of propane at about 3 AM and just didn’t want to hassle with stopping at the next truck stop to refill the tank. That stretch barley made 13 MPG.

I have seen a lot of Talk about what propane does or doesn’t do. All I can say is that in my case I saved in order of $150 in fuel on one trip to the west coast as a result of the propane.

Pulled most of the Mountain out of the Grape Vine on I5 @ 55 MPH in 3rd Gear. Toward the top I backed out of the throttle as the Transmission Temperature gauge reached 220 F and Engine just over 200 running with about 8 LBS of boost.

I will do a write up of my DIY propane in the performance section.
http://www.dieselplace.com/forum/showthread.php?t=315409

Bone stock, my Yukon avg was 18mpg. After the lift and 35's with the stock 3.73's my avg is 14. I haven't ran a tank through it since I changed injectors, and exhaust. I will post it as soon as I know.

My family and I went on holidays this week. We went from Red Deer AB to Victoria BC and only put 110$ at 83-97 cents per litre. we have put on approx 1500 kms and averaged 23-24 canadian mpg. Amazing since if you comvert it to gas mpg using the prices at the pump, thats 26-27 mpg. My dads 2006 5.3 only gets 20 if heès lucky, and this truck of mine pulls wayyyyyy better. First day I had it I was pulling a 14000lb loads of sand around

I think I'll add my truck up to the list:

CC/LB/SRW, 4.10 rear, canopy, ******* Turbo, 3" downpipe into a 3" constant that goes to cab end, then into a 3" turndown, "Somewhat" high flow air filter, Knife's edge intake manifold, 67,000 miles

:DOn the Highway she just did roughly 18mpg average coming back from Pittsburgh, PA :D

About 13.5 mpg average over the last 2 years since I started monitoring it.

About 12-13mpg city, 15 mpg highway, but since I do mostly city and off road driving, that pushes the mileage down.

This is on a GEP Block 6.5 Turbo, stock everyting in an 98 Hummer.

Unloaded drove from Houston to Fort Smith, Arkansas averaged 24mpg. 5 speed manual and 3.43 rear gear regular cab longbed. Oh and the back tires are oversized at 285/75R16.

I installed the factory replacement style K&N air filter in my Dmax and I picked up 1.5 MPG. The acetone does work we tryed it our PowerJoke (7.3) and it picked up 2 MPG (over 10% increse) (fuel lubertcant recomended). The tornado on the other hand is a joke anything in the air stream to "change direction" of the air is only a restriction like a dirty air filter. We have tested this at my college (it reduced fule economy).

Quote from the linked thread.

you can't bash the powerstroke i know it has the ford logo on it but it's far from a ford product and has way more balls than a 6.5 ever thought about and i'm not bashing the 6.5 and if it's compared to the dmax the dmax might have more power but which one is more reliable i really like the way chevys look and drive but there is no comparsion to a 6.5 and a 7.3

Reading the entire post, look that I have the worst efficiency engine.
My 94 Silverado, long bed, 4x4, auto, 3.73, 285/75/16 give me around 11 MPG on town, but the streets on my town is up and down and a lots of stop and go.
I have to keep spending money and changing components, I got my truck on an auction, when I just got the air filter was plugged with mud (is correct the air filter with mud) the oil on the engine was real dirty, few day later the injection pump fail. That give an idea if the previous owner never take care of the truck.


Regards

Actually the ScanGauge 2 is so "real time" that you almost can not hold it steady to maintain a good mileage number. It needs about a 15 second average in order to be able to use it like that. Even when my cruise control is on, the MPG number changes when the wind gusts change and with the slightest change in grade. You have to stare at it for a while to get an "eye-ball-average". Of course you can look at the average mileage for the tank so far. All of this is only valid if you've got it calibrated and I'm still working on that on my third tank.

It's a good instrument, don't get me wrong. It's still being improved and I'd still buy it. Why, just tonight on the way home while fiddling with my new TorqLoc I managed to piss off the PCM and brought up the SES light. I then proceeded to call up the code on the ScanGauge. wrote it down, cleared it and got the transmission out of limp-mode, all while running along at freeway speed. Sweet. Mike

Using the instructions, I customized mine so it always displays mileage of your current trip (since the last time you started it) as well - it does make it useful for on the fly adjustments. Also, even though the real time MPG changes rapidly, you can still get a good sense of where it is and if the numbers are relatively low or high.

Reading the entire post, look that I have the worst efficiency engine.
My 94 Silverado, long bed, 4x4, auto, 3.73, 285/75/16 give me around 11 MPG on town, but the streets on my town is up and down and a lots of stop and go.
I have to keep spending money and changing components, I got my truck on an auction, when I just got the air filter was plugged with mud (is correct the air filter with mud) the oil on the engine was real dirty, few day later the injection pump fail. That give an idea if the previous owner never take care of the truck.


Regards


Don't feel alone, I'm right there with you....11, 12, 13 mpg or so

I finally did my first fill up over the weekend, and my mileage was 20 mpg, which pretty much matched what the scan guage said - this was great considering that the truck that this one replaced only got about 12 mpg!

Before the lift and on 235-85-16, I drove Miami to Castine, Maine and averaged 21 mpg at (70mph). after the lift and tires I did a 200 mile trip and managed about 18.2 (63 mph and babying it). The truck has 4:10's, so i don't think the tires hurt as much as they could have. I hope to try to increase the mileage in the next year. (Chip, Exhaust, new injectors, shorter tires). I would be happy to be back in the 20's.

me too..i average about 13 running 295's.

Don't feel alone, I'm right there with you....11, 12, 13 mpg or so

me too..i average about 13 running 295's.

Did you compensate for the tires when calculating your milage?

Did you compensate for the tires when calculating your milage?

unfortunately yes...

im only gettin about 10 to 11 most of it being town

I got just under 15MPG pulling a 2500LB open trailer through Ohio and West Virginia. Quads and Dirtbikes on the trailer. Mostly highway 65-70 MPH. Ive got 3:73s and mild 265/75/16 tires. It ran between 3 and 6 lbs of boost max. I have the T/M backed off for mileage because when I was making 9-10 max it would make 4-5lbs highway boost (empty) and mileage went to the crapper. Around town I get about 16.5 MPG with average driving habits. Haven't had it on a long trip empty yet so I don't know what it will do in that case. It needs an alignment too and I know that can have a pretty big effect on mileage.

to get the same power from a gasser ud be running a 454 and getting less than 5 mpg. im buying a 6.5 cause it gets close to the same milage as my little chrysler with a 2.4L and i need a truck everyother weekend...my old f250(s) were dog(s) on gas and were gutless. and ive driven a 6.5 and its a little on the slow side but driving 100KM a day (just to work and back) im sure ill see fuel savings compared to my 4.3 tbi(under 15mpg) my 305 camaro (hasnt been running long enough) or a gasser pickup(old f250's = 11mpg or less)...6.5s were not aimed at the power market there more of the towing slash economy engine and im fine with that.

just a report.. still averaging 11.6-12 and thats it.

Just filled up again at the same pump all empty driving mostly city with about 20-30 miles hwy. Got 17.2 MPG.

I read all the posts and can't find what I am looking for.

I just purchased a 96 K2500 4wd extended cab longbed in great condition, 190k. It has the dark blue paint, Silverado pkg and is one of the cleanest paint/interior trucks I have seen and I stole it for $750 bucks. :) It failed emmissions and the owner did not want to pay to even get it checked. It turned out to be a broken vacum line to the wastgate, so no turbo.

The kicker is, it's a 5-speed tranny. From what I can tell, there are not many of these.

I have the 4:10 gears. At 75mph, the engine speed is around 2,500 rpm.

What kind of mileage should I expect on the highway?

What I would love to see is posts that show:

Year and Model:
Speed:
RPM:
AVG gas mileage:
Tranny:
Gear Ratio:

If each of us post those 6 simple things, the community will easily be able to compare apples to apples. We should keep it specific to highway travel, unloaded since load sizes vary. With the avg speed you like to travel, the rpm at that speed, your average economy, auto or stick and your gear ratio in a simple line item format, we will be able to compare each of our trucks.

Im excited to be a 6.5L owner now. :)

My truck:

'96 Extended Cab SWB Heavy Half-ton 4WD
Auto. trans.
3.73 gears
6.5 unmodified

My unladen highway mileage has remained around 17.5-20 mpg (all high altitude driving above 5,000 ft. elevation) since I bought the truck used 11 years ago--IF I keep the speed 65 mph or under. Go 75 mph on the Interstate and the mileage will drop by about 2 mpg.

I do have one possible disagreement with the very first post on this thread where it states that diesel engines use more fuel at idle than gas engines. Huh? One of the main advantages of a diesel engine is that it generally will use LESS fuel at idle than a similar size gas engine. The use of fuel injection on gas engines has narrowed that gap some, but diesels can idle on a much leaner fuel to air ratio than even a fuel-injected gas engine can manage, not to mention that fact that diesel has more energy per gallon than gasoline. I don't recommend any unnecessary idling, but a diesel should use less fuel than a gas engine when it does idle.

XM-5 Though one end to the other in my truck gave me 1.5 MPG:rolleyes:
Lucus probly the same.

Bringing this thread back to life.

I've been averaging around 12.8 around town and just under 14 on the highway.

Looking for ways to get it higher..

You really need to get rid of those 4.10 gears.

Either that or drive by the gauges and not your speedo. 1800 RPM is the sweet spot. That boils down to about 55 MPH.

As my engine is fresh again. I find myself driving with less boost but still good power and great mpgs. I have averged 19 mph. That is combo of city and highway driving. There is no problem with boost just I am making better power altogether so I am running less pedal, that makes for less fuel,and less boost.

So if your mpgs are down how is the health of your engine? I didn't like what it cost me to go through my engine. But I do like how it turned out.

You really need to get rid of those 4.10 gears.

I sold a parts 1500 'burb last month that was 8lug with 3.73 gears. I did seriously think about swapping the rears before selling it, but in the end decided to stick it out with the 4.10s. I do plan on buying a large camper to tow sometime soon.

What kind of MPG difference do you think a gear swap would make? 2-3 mpg? more?

With 4.10 gears and a th400 you just cant get good fuel mileage with these trucks.

Doing a radical 4.10 to 3.08 gear swap would net about 25% more milage. Depending on what you start with that could be good for at least 3mpg easy.

I topped out at 27mpg with 3.08 gears (not drafting). My truck chugs along at 1,250 RPMs at 55mph with its TH700 trans. I also have great top speed, no problem getting to 85mph on flat ground (then MPGs drop to about 18mpg).
Going from 4.10 to 3.73 wouldn't do much, maybe +1mpg or a little less. Going with a 3.23 or 3.42 might be a good middle ground and could provide +2mpg with out hurting torque much. If you drive a lot of highway miles unencombered then 4.10s are really a waste.
I do plan to do some light towing with my truck and its 3.08 gears. Most I ever towed with the old 6.2L set up was about 6,000lb and was thankful it was a flat nearly hill-less trip.

My truck is set up for highway driving, I know that is not what every one wants but I made sure to start out with a truck that had a 6.2L, 2wd, th700 and prayed it had 3.08 gears. I would like to be able to hit 30mpg with the new engine after it is turbocharged and water injected. Also a dirt road is about the limit of my off roading.

With 4.10 gears and a th400 you just cant get good fuel mileage with these trucks.



My 'burb is a 1996 and has a 4L80E transmission.

My cucvs have the TH400 and all but the M1009 (mil blazer) are 4.56 gears.

4l80e, 4.10's, i average like 13 city and highway combined

i also dump in a quart of west marine premium 2 stroke oil at every fill up

The 4L80E is the updated Th400.
Gears and inner working above the valve body are largely the same.

So over the last 5 tanks of fuel I've put in my truck since the new engine, I have averaged 18.3 MPG. On the last tank, driving from Salt Lake City to Stateline, NV via Carson City, I got 20.1 MPG. I think I was getting better, but the climb up the mountain from Carson City used a lot of fuel. Going 45 MPH, I couldn't keep the EGT's under 700* and I saw EGT's of 900*. It killed me to see sustained EGT's that high. I'll see if I can keep it under control today when I come back up from Carson City.

I have some MPG numbers for the first tank of fuel for my new engine.
I had the truck loaded down with tools and parts, with a 24 foot lader on top and pulling the utility trailer (mostly empty) I got alittle over 21mpg.
Not bad for an engine that wasn't even broken in.
Near and above 3000 feet this engine (non turbo) cant mantain speed with out higher EGTs.

Hi All,my motor coach weighs just at 16,000 lbs empty,then a full tank of fuel (60 gal) plus my compressor,propane tanks,tools,clothes and spare parts,probably a total of 17,000 lbs. on a trip last summer,i averaged 10.79 MPG, over 6209 miles. i maintain 55 MPH,using cruise control, i try to stay about 50 yards behind a semi (not always possible) and with the 4L80 auto trans,i have no engine back pressure to slow me down,so when im approaching a traffic lite,i shift i nto neutral, (and hope the light changes) so i dont have to stop....every little bit helps...

Hi All,my motor coach weighs just at 16,000 lbs empty,then a full tank of fuel (60 gal) plus my compressor,propane tanks,tools,clothes and spare parts,probably a total of 17,000 lbs. on a trip last summer,i averaged 10.79 MPG, over 6209 miles. i maintain 55 MPH,using cruise control, i try to stay about 50 yards behind a semi (not always possible) and with the 4L80 auto trans,i have no engine back pressure to slow me down,so when im approaching a traffic lite,i shift i nto neutral, (and hope the light changes) so i dont have to stop....every little bit helps...

Transmission lube is based on engine speed. When you shift into n you drop rpms to an idle so most of the lub drops off. Is your $2000 trans worth even 1 mph?