I have been trying to get a handle on my fuel mileage. I have noticed that I get quite a bit of variation from one tank to the next. At first I was thinking that it had to do with the brand and the cetane number. Now I am leaning towards the way that I drive. I usually drive on the easy side, but I have been running some test that involve trying to get up to speed quickly (rpms around 2600 or more) then running in high gear at low rpm. This seems like it is working better. All of my driving lately is within a 10 mile radius from my house and although I haven't refilled and checked my mileage on this tank, it looks like it is going to be great. I have been 225 miles and it is not quite down to the half yet.


Kirk

Mileage in my mind is so subjective. Too many variables. I see mileage posted all over the place. Most get much better than me. I average 12-14 winter driving and 14-16 summer driving. I think it is the kind of math they use to figure it. Liars figure, but figures don't lie. I think a lot of people estimate. The DIC in mine is not accurate, off by about 1/2 mile per gallon, worse when trailering. I haven't reset the DIC since new, have towed probably around 6000-7000 miles, run in 4x4 a little and my average for 18K miles (according to the DIC) is 13.2 mpg. I don't run hard, but don't baby it either. No mods - completely stock. Best tank was a little over 17 mpg, worst around 5 mpg (off roading). I do mostly surburban driving, a combination of stop and go plus some freeway. Never all one or the other. The way I look at it, 16 for a truck of its size and abilities isn't bad.


So what do I do when its empty? Get out the card and fill it up. Ya ain't going to improve the fuel economy after you burned the fuel.


Just my .02 for you thoughts.

I just updated my spreadsheet with current info.

It's nothing fancy, though it does show that my typical "around town" mileage is a bit better than 17 MPG, and my towing mileage is ~13 mpg for a smaller trainer and ~11 mpg for the travel trainler. See the graphs tab for fuel cost trends and mileage.

Look at the raw data and you'll see I have included my indicated mileage. Indicated is always higher than calculated, most especially when towing. This is also shown in the graphs.

I now see that my towing mileage is much lower after adding the Edge/Juice combo. I'll have to do some towing with it removed and see if the mileage goes back up.



2004-10-11_220105_DieselFuelRecords.zip (uploads/HBruns/2004-10-11_220105_DieselFuelRecords.zip)

Are you filling consistantly? fill to where you can see liquid fuel in filler neck, and you will always be within ozs. of the same fill. Use the trip ODO & not the DIC.





I use a spreadsheet I cribed from one of the guys here awhile back. It tracks all the costs involved & is really sweet. Wish I could remeber who did it - I'd give credit. He had it available for download on his site, and it is one of the nicest I've seen.

I think one of the problems is that diesel foams when filling. After the pump kicks off I have started to wait about 15 to 30 sec for the foam to die down and then fill again to kick off. Doing this a couple of time seemed to make my reads a little more consistant.

Does foaming really make that much of a difference? I have been
filling to the top of the neck. Can't squeeze two or three cents
in.



But when you put in an amount, make sure you check the milage
driven. The driven milage will be down, but so will the volume of
fuel. Should still equal the same MPG's



Still my line of thinking may be out to lunch.

Hbruns,


Your fuel mileage is excellent. Can you disclose your secret? Thanks for sharing.


Kirk

I can't say if foaming will make that big of a difference but it will have an impact. I have always hand calculated my milage - it's a sickness I tell ya. Anyway same trip, same path, same same. One time I'm getting 18.-- and the very next tank I'm getting 12. My avg has always been 16ish on these trips. Now if the fuel foams and I was only able to get 28 gallons in but I had really used 29 thats going to show up as better milage. Now my next fill up if I get the right amount in, I won't have traveled as many miles so it would show up as lower milage. Is it the diesel foaming? Hell I don't know for sure but it was the only way I could account for the swing - And the fact that if I added them together the result is what I normally get on that trip. My normal milage city/freeway is 14-15. All freeway pulling my trailer is 16ish which is way better then my 460 so I'm happy and will probably quit checking it.

Mightyvh,


That is exactly what I am talking about. You think you got it figured out and them bam 13mpg.


Kirk

Hbruns,


Your fuel mileage is excellent. Can you disclose your secret? Thanks for sharing.


Kirk

I don't know if there is any secret to disclose. I do try to keep a steady foot on the accellerator. I always take it very easy until the engine warms up. Since I instaled the Edge/Juice, I try to keep my foot out of it.... mostly. http://www.dieselplace.com/forum/smileys/smiley2.gif

Other than that & the stuff I have listed below in my sig, the truck is stock.

The Ford 6.0 seems to be all over the place on milage, but one thing that has been clear is the sweet spot for that engine is around 1700 - 2000 rpm. 2000 rpm w/ either the ZF or the 5speed TS is right at 70mph. This area will yeild the "best" milage (somewhere between 16 & 22). This is with the 3.73 rear end.





Do you guys know if the Dmax has an area like that? I haven't seen anything in this post so far. My friend tells me his 01 Dmax gets right at 19 if he's empty, and towing his 11k 5er he gets about 14. That seems pretty good to me.

Maybe 1800 to 2000 RPM's is about the best that I have found, so far.

I have been trying to get a handle on my fuel mileage. I have noticed that I get quite a bit of variation from one tank to the next. At first I was thinking that it had to do with the brand and the cetane number. Now I am leaning towards the way that I drive. I usually drive on the easy side, but I have been running some test that involve trying to get up to speed quickly (rpms around 2600 or more) then running in high gear at low rpm. This seems like it is working better. All of my driving lately is within a 10 mile radius from my house and although I haven't refilled and checked my mileage on this tank, it looks like it is going to be great. I have been 225 miles and it is not quite down to the half yet.


Kirk





One reason that some see lower mileage around town is that the engine is less efficient when cold; My guess is that when you are "romping on it" - you are getting it up to operating temperature faster. Normally takes mine a few miles to reach full operating temp and higher efficiency.


On short trips, I guess if I had a choice between better fuel efficiency and "romping on it" before it is completely warmed up - I'd probably opt for burning a little more diesel...


- jeff

I've found that keeping my 01 Duramax between 1700-2000 rpm yields the best mileage; 18-21 mpg depending on outside air temp. It's not completely stock though, has K&N air filter and 5" exhaust.

If I can stay off the accelerator and hold my rpm's below 2000 on the freeway-where most of my daily driving occurs-I can get 19 mpg or better. My best is 20.5 on an engine with over 90,000 miles on it.


Did I say I LOVE THIS DIESEL???

My 01 Duramax is getting me about 14-15mpg. The truck has a 6in lift and 285's. Anything I can do to increase the mileage? Would much rather have 18-19 on highway, like I thought I would get when I bought the truck.

OK guys, I just bought my first Diesel. A durmax of course. I had 285's on my gasser before this and really liked the look of them.


Does anyone have the real deal on what 265's, and 285's will do to my mileage in the city, and on the hwy EMPTY, not towing. the taller tires should lower the rpm's while the heavier tires migh use a little power up. Just to confuse things a bit more, would a chip, or programmer help negate the extra fuel that's consumed while turning the larger tires around the city?


Any experiences with similar tire size comparison?


thanks,

My 'Max has a sweet spot at just a hair over 2,000 rpms that seems to get me the best mileage. This put me just a hair under 70 mph on the highway. Mileage numbers seem to drop off as the average rpm's increase. Edited by: Silveradogs

My truck has 265/75's on it. Empty I get around 18 city and 20 highway, all calculated by hand and correct for tire size. Sweet spot for me is betwen 2000 and 2200 rpm. As my dad found out, driving it at 85 mph takes fuel milage below 15 mpg highway.


Here's a question: I have a CC/short box. I thought the fuel tank was 24 gallons. I was in Canada yesterday and wanted to wait till I got into US to get fuel. Gauge read just under 1/4 so I wasn't too worried, even though I was over 440 miles on that tank. When I got to the first gas station, I put in 23.3 gallons!! http://www.dieselplace.com/forum/smileys/smiley3.gif I had gone just over 470 miles. Is my gauge really that messed up? Shouldn't the low fuel light have come on anyway? Any thoughts?

My friend tells me his 01 Dmax gets right at 19 if he's empty, and towing his 11k 5er he gets about 14. That seems pretty good to me.





Best I have gotten towing a 7000# travel trailer is 11. Usually around 18-19 empty except for 1 long trip where I ran about 65 and got 21. Anyone who gets 14 towing either has a great truck or his arithmetic needs some work.

Here's a question: I have a CC/short box. I thought the fuel tank was 24 gallons. I was in Canada yesterday and wanted to wait till I got into US to get fuel. Gauge read just under 1/4 so I wasn't too worried, even though I was over 440 miles on that tank. When I got to the first gas station, I put in 23.3 gallons!! http://www.dieselplace.com/forum/smileys/smiley3.gif I had gone just over 470 miles. Is my gauge really that messed up? Shouldn't the low fuel light have come on anyway? Any thoughts?





My book says 26 for the short bed and 34 for the long. Wish I had a bigger tank as I can usually only go about 220 while towing before I need to fill up. I need one of those monster 45 gal. tanks so I can spend a $100 on a fill up. Who would have ever thought that?

The effect of taller tires is generally to decrease the torque
available at the the road. Same as if you changed your rear-end ratio
from 3.73 to 3.50 or thereabouts. By increasing the radius from the
axle centerline to the road, you are increasing the amount of power
required at the axle to achieve the same amount of power at the road.
Using more power means burning more fuel. This works in reverse on the
brakes- the larger radius gives the tire a bigger lever to apply
against the disc, so your brakes require more clampnig force to produce
the same amount of braking at the road. This heats them up more
quickly, and reduces the total amount of brake force available. Adding
to all this is the extra weight of the larger tire being farther from
the axle centerline, requiring even more energy to accelerate and
decelerate whenever the truck is moving.This is compounded on a lifted
truck by the large increase in in drag created by putting the
suspension directly in the airstream. Drag increases exponentially with
speed, so if you double the speed, the drag goes up by a factor of
four. (Drag at 50mph is four times as great as drag at 25mph). Most of
the energy spent cruising at 60 is overcoming drag, so, if you increase
the total drag by about 30-40%,... guess what? MPG suffers mightily.



So, you can see that increasing the tire size and lifting the truck has
a LOT of effect on mileage, braking, and perceived power available at
the road, even though the engine is producing the same power at the
flywheel. EVERYTHING has to work harder to stay the same as with stock
tires.



With all that, I do believe I've talked myself out of a tire and wheel upgrade....http://dieselplace.com/forum/smileys/smiley19.gif



Steve

Talking to yourself is okay as long as you don't answer. http://www.dieselplace.com/forum/smileys/hihi.gif

-That's what's worrying me... my self will sometimes answer mehttp://dieselplace.com/forum/smileys/hihi.gif.

But, seriously, most people don't think much about slapping on a set of
giant tires and jacking up the truck, and are then surprised by the
fact that it won't get out of its own way, gets bad mileage, and won't
stop! They usually don't figure out the stopping problem till they hit
something. Hopefully an inanimate object..

I don't know what the math says but I just took off my 285's because I thought I could get a little better mpg by going to 265's but thus far I've noticed no real differencem except the truck handles better with the 265s.

wlkjr: I have 50 gal in bed tank plus oem...76 gals total. I was up in Maine few weeks ago and let tanks get a little lower than I like..............$141................ to fill up. Who would of thought!

I have K&N filter and 285-75-16 BF.Goodrich TA KOs . I installed a Bully Dog Pup on my Truck and have it set on the 80 Hp. and set the tire size to the proper height and I am getting 75 miles more out of a tank of fuel , 26 Gal. Tank . 2002 GMC CC D/A 4/4 http://www.dieselplace.com/forum/smileys/smiley16.gif


Try the Pup yul like it