dissonance

The stock tire size on the truck was 245/75; I have since installed 265/75... I never monitored the gas mileage before the tire change… but with the 265/75 I’m getting around 10mpg I have seen as low as 9…

The dealer told me moving up in tire size would not change anything? They also told me the computer would lean the bigger size? I have a hard time believing that… I have a 98 camaro and I know with a tire change you must change the shift points ect…

It’s a 6.0L with 4.10’s I think? Autotap show 3.98 for the gearbox… ltrims are in good shape “-1%” truck has around 3000miles on it…

Is this normal for the 6.0L trucks? Or is something wrong?

Trevor @ Texas Speed & Perf.

iTrader: (3)

I did the exact swap that you mention on my '02 2500HD 6.0L, and my gas mileage was unchanged with the 265's vs. the stock 245's. 9-10 MPG sounds a little low for in-town driving, but it totally depends on your driving habits. With normal driving, I've been seeing right around 12 MPG or so with all in-town driving. I see 12-12.5 MPG at 70 MPH when towing 5,400# of car and trailer @ 70 MPH. I've yet to take a trip without a trailer behind me. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

As for the tire height, the computer will not re-learn the added height. The dealer is an idiot. You need to get a Hypertech Power Programmer 3 (or something comparable) to change the tire height and get your speedo back on track. I programmed mine for a 31.5" tire height, and it seems to be right on.

Your gas mileage seems a little low at 9-10 MPG, but it's very possible if you're an aggressive driver. FYI, my truck has the 4.10's as well.

Trevor