Got A 05 Duramax also have a set of 285/75 BFG all terrains I was planning on putting. A buddy of mine thought he seen A post where a guy put 285's on a duramax and lost nearly 5 MPG?? the 285's sure would look good but its not worth 5 mpg to me. Can anyone back this up or have diffrent results?
Thanks Larry

 

I put bigger tires on mine and did not notice anything like that big of a difference.

 

you wont notice that much maybe 2mpg tOPS!