What?

Hmmm, I've NEVER got more than 21 MPG per Canadian gallon, or 17.5 MPG US....

 

Cool. Guess a front end lift is needed for them to fit.

MikeyB

 

The effect of 315s has a lot to do with where you are on the rpm/mileage curve at your typical road speed. Tests have the Cummins optimum mileage at 1750 rpm, but its pretty flat till about 2100 rpm where it drops off steeply. For 05-06 G56 trucks and 410s, 65 mph is on this steep slope, so doing anything to reduce the rpm has significant effect on mileage, even with a bit more rolling resistance. The mileage increase is usualy 7-15%. However, you can go faster with 315s at the same rpm, so many drive 70mph instead of 65 and that additional road speed eats into the mileage gains. So you will hear mileage numbers all over the place. Although I didn't go with the larger diameter tires for mileage, I drive 5 mph faster with the 315s and get a 10% fully corrected mpg boost.

 

Is there really that big a difference between the auto's and the hand shakers. I'm turning 2000rpm at 72 mph, auto with 3.73's and stock tires.

 

theres not as much of a difference with 07-08s as there used to be with 06 and older

 

Looks like 3.42's and a G56 is a little better than a NV5600 and 3.73's is... I run

1938 @ 65
2087 @ 70
2236 @ 75

When I got to 285/70's this weekend it will read

1876 @ 65
2020 @ 70
2165 @ 75


So far I dont mind the 3.73's with the NV5600 .73 6th, in fact when towing about 65mph I wish I had 4.10's or the .79 6th the G56 has.... I guess a GV would fix that

 

Any body ever consider running the 235 80 17 tires? that seems to be slightly larger diameter than the stock 265's and smaller width for hopefully, better mpg as well as winter traction.

Anyone?

 

Not enough to make a difference - 31.8" vs. 31.6". This is less than a 1% differance.