*The Official MPG Thread***

knkreb · May 20, 2008

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.

acesneights1 · May 20, 2008

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.

gonnasellit · May 20, 2008

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.

instarx · May 20, 2008

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

Kartoon · May 20, 2008

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.

adamguy2006 · May 20, 2008

McRat said:
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.

arkredneck · Oct 15, 2009

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

knkreb · May 21, 2008

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

instarx · May 21, 2008

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)

fasteddie1_2003 · May 24, 2008

fuel mpg

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.

cretan · May 26, 2008

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.

jbsaxman · May 26, 2008

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.

odlaw · May 29, 2008

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.

oil pan 4 · May 30, 2008

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.

cretan · May 31, 2008

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.

turbovanman · Jul 15, 2008

Do you know exactly how much you picked up?

oil pan 4 said:
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,

Censored

jbsaxman · May 31, 2008

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

oil pan 4 · May 31, 2008

"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.

cretan · May 31, 2008

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.

knkreb · May 31, 2008

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.

cretan · May 31, 2008

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.

oil pan 4 · May 31, 2008

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.

knkreb · May 31, 2008

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...

oil pan 4 · May 31, 2008

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

cretan · Jun 1, 2008

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

GM Guy · Jun 11, 2008

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.

Texas Diesel Guy · Jun 27, 2008

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.

IamDave0887 · Jun 27, 2008

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.

Texas Diesel Guy · Jun 27, 2008

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.

Pruittx2 · Jul 1, 2008

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!!!

*The Official MPG Thread***

Our Vendors

Top Contributors this Month

Recommended Communities