I have been reading the latest Diesel World while my wife has been in the hospital and it brought me to wonder some things. They are doing some testing with a 6.0 and mileage. Im sure some of you have read it. Anyways they upgraded the tire size from a 255/75r16 to a 305/70r16. That resulted in a 1.7 inch increase in tire size which caused a speedometer and odometer error of 5.6 percent which meant that the speedometer and odometer were reading low. So my question is if tire size is causing the odometer to read less than the actual mileage that means that my calculations of 13mpg is off by alot. This also means that when my speedometer reads 70 and Im sitting at 2k rpms I am actually running 65mph or so correct. The article doesn't say what formula they used to figure this out so does anybody know? They are also claiming 24mpg with a bed cover, exhaust, intake and xzillaraider chip. Sounds pretty good to me. What do yall think.