Fuel Mileage

[Destroyer]

I have a 2007 crew cab 2500 HD 6.6L turbo mated to the Alison transmission, I have been real light on the gas peddle however after 1462 miles I have burnt up 139.9 gallons of fuel or 10.45 miles to the gallon. I did pull a trailer 8400 pounds 300 of those miles. It also did a trip unloades 150 miles. Does this sound right to anyone? I was told to ecpect 17-20 mpg. The truck came with a 4 inch RCD lift and a corrected speedo turning Nitto 295 70r17 any ideas? or is this what I should expect to see?

[Mark Rinker]

Its very possible to see mileage in the 10-11 range while towing, but mostly with heavier loads and/or tall, oversized loads creating large wind resistance.

If your calculations are correct, I'd guess that your oversize wheels/tires are the culprit. Did you do alot of start/stop driving with the load? That is when your truck will really struggle. At what speeds do you cruise? Top speeds?

Drive more unloaded, and establish a baseline of that mileage. I'd guess you are going to see low to mid teens. Your truck's ECM fuel map and TCM shift points are all calculated on the assumption that the tire diameter is a constant - and factory stock. Departures from that will most likely drop your fuel mileage, regardless of how light-footed you are.

The price of stylin'!!!

[Destroyer]

I went the speed limit or a little below that. Low to mid teens would be great as opposed to 10.4. I do 65 max never faster than that. I will set the trip meter and fill it up and see what I get the number I used were right off the trucks dash meters. When I bought it the salesmen and a few freinds said 18-20 so thats what I would expect to see not Shiek enriching 10, that is what made me wonder if there is some thing wrong or maybe the turbo eats more fuel which I understand should be the opposite. Thx for the reply.

I'd guess you are going to see low to mid teens. Your truck's ECM fuel map and TCM shift points are all calculated on the assumption that the tire diameter is a constant - and factory stock. Departures from that will most likely drop your fuel mileage, regardless of how light-footed you are.

It said on the window stickertire size was corrected for so I will ask to make sure that happened, maybe it was left off, but that is a great point thx. If you are saying that no correction can be made for the tires Dave is gonna get a butt chewin LOL. But it had the RCD 4 inch lift as stated with correction for the tire size and gears to match in the read end. 295 is not huge however. But I did notice it shifted hard a few times both light and towing.

Any ideas on a chip for it? or will that void the warrenty? Will a chip actualy help mileage?

will putting a propane system on here void the warrenty, I wonder out loud ?only because I don't like to read warrenties.

I also have 1984 retired military blazer with a 6.2l it is going to be my plow truck, but thinking of a 6.5l swap and a propane system if I can find one for it.

[Mark Rinker]

First things first. I would enquire as to what was done to 'adjust' for the taller tires. I am betting they simply corrected the ECM so your speedometer and odometer will be accurate. I doubt they swapped gears, which would be the only way to mechanically correct for the taller tires.

Since your truck is brand new, I'd let it get broken in before worrying about mileage. Most owners report their mileage improves over the first 10-15K miles. You should do some quick oil changes and also change out the rear diff after this initial towing, regardless of miles on. A good time to switch to synthetic in the diff. This will also help with mileage.

As for chips and propane use, I'll let you do more research on this and save my opinions. It has alot to do with what you plan to do with the truck, personal preferences, pocketbook depth, etc. Rememeber that a diesel needs to breath, not just burn more fuel to make reliable power.

Your brand new LBZ is no slouch, right out of the box. You might want to break it in and get to know its intricacies before pouring the coal to it...

[Destroyer]

Good advice as I was not thinking of the oil change, any recommendations on the diff oil?

Double checking it, yes corrected the speedo but still has 3.73 gears.

Good on you. I will break it in like I have been no high speeds ect, other than the small bit of trailer pulling I did. When I took it on a test drive the salesman said "Romp on it" To which I replied "no thx". I am 42 have done 145 on a street bike and faster in a Camaro I have out grown the need to romp, not to mention romp a brand new truck. Good thing I took it away from those romp happy salesmen. Besides 1/4 throttle feels like a pretty good romp to me from a dead stop even my buddy said the same thing after launching it he said " Honest I barely touched it" I knew he was not liein' . It is an awesome truck. My plans are to pull my Fifth wheel to Alaska and a trailer to move our house hold items after ward. 22k of pull should mean only two trips. My plans are to keep it for at least 10 + years it is my retirement truck as it were. To think I wanted a H1 Ha as if.

[Kennedy]

When you lift and put big tires on you will definitely see a reduction in mpg due to wind load etc.

Verify speedo with a GPS and/or the Odo against 10 or more mile sticks and you can then calculate the percentage of error.

[Tough Guy]

Its possible with winter fuel you are seeing slightly lower fuel economy than the higher numbers you were quoted when you purchased the truck....

I see 18-19mpg in the summer, in the winter I generally see around 16-17mpg...so between your lift/tire combo, new engine, and winter fuel....your mileage will suffer.

Chris

[Destroyer]

I feel better already