I have a 2003 6.0 i bought it with 43,000 miles on it, the truck now has 85,000 miles on it and hasn't given me a problem. It's got 4" turbo back exhaust,AFE cold air intake, and The Bully Dog Triple dog chip and monitor...Hasn't let me down at all. All the power in the world, runs down the interstate getting 21 miles to the gallon. 12-14 with a four place sled trailer, same with 5 tons of hay on a car hauler trailer. Now my 2004 6.0 company truck has 162,000 on it, tranny is starting to go, replaced 6 injectors, and a EGR cooler. Gets about 16 mpg or so, I haul a lot of stuff in the bed it weighs out at 10,000lbs. What I've been told by the mechanics is the 6.0 is a very finnicky motor, you have to be regular on all of your oil changes and filter changes. I guess it's all in how you take care of them.