my buddy has an 05 duramax cclb we recently put a 4 inch lift on it with 285 series tires and everything and he had the computer recalibrated at the dealer and his fuel mileage is reading on average of 11 mpg. I was wondering if someone has a similar set up and could tell me what they were getting his just kinda seems low to me. ooo and the oil presure at idle is like next to nothing is that common? thanks for everyones time