gas mileage
 

I am sure it has been ask BUT 2001 HD 8.1, is this normal....8 miles to a gallon? I could live with 10 but 8 dang
Truck only has 66000 miles on it and yes it has the allison with 4/11 gears
Any advise thanks

Re: gas mileage
 

I just drove from MN to TX and averaged 12.5-13 mpg every single fill-up.
My only difference from your config is 3.73 gears, and that does make a difference.
3.73 was standard for your config, 4.10 optional.

Re: gas mileage
 

mmm...2006 Silverado, 5.3...4WD....

gets 17 average across entire vehicle life....

drops a little if I tow my 24 ft tri axle enclosed toy hauler...

but 8 !!!!! give ma a break !

Re: gas mileage
 

It might be worth the effort to take it to someone that can check all the specifics in the engine tune.

Re: gas mileage
 

2005 2500HD 6.0 4L80E NP263HD 4x4 4.10 axles and 265/70R17 tires. 12 rural 2-lane 14 interstate.
3.73 would definitely give me better mileage but the 1" larger tires help some.

The 8.1L with 4x4 and 4.10 axles along with stock 245/75R16 tires will not do well on fuel. I'd expect 8-10 city and maybe 10-12 highway if you're lucky. It'll pull like an ox team tho.

Re: gas mileage
 

HA! :waah: Yes, that's normal ... have a buddy with 8.1 2500 Suburban 4.11 and that's what it gets too. Was jealous of them at first for being able to find a 8.1 Sub, our 2500 Sub is a 6.0, until I realized the difference in MPG.