2009 2500 6.0 w/auto real world fuel mileage
 

A friend of mine is looking to buy a 2009 Chevy 2500 crew cab with the 6.0 with the 6 speed auto. He does not have a computer and was wanting to know what the actual fuel ecomomy is. The salesman is trying to get him to upgrade to the diesel. According to the salesguy the 6.0 might get 12 mpg and the diesel would get 19-20. He might pull a trailer a couple times a month but mostly it would be empty.

that's about right, diesel does get better mileage but you need to do the math to figure out if it's worth it. For instance base it off $1.00 difference in fuel prices, figure how much you spend a mile, tank size times the fuel cost then divided by the MPG. then figure out how long it would take with the amount of miles you drive to start saving money from the base price since diesel trucks are much more expensive. If he drives A LOT during a year it won't take long but average I did it before and it would take 6 years to start SAVING money by buying a diesel.

I am running the gen IV head on a 6.0L and my milage is around 15-16.

I don't think the engine or anything has really changed from my year. I have the 6.0/6L90E combo and got around 15mpg 80% highway driving(70-80mph) :D It didn't drop much for mixed driving.

Thanks for the info. I will tell him today.