I've got an '03 Hemi with new exhaust 2" (?) into the muffler then split into dual exhaust. I put an air intake in as well as a throttle body spacer, and get 20 mpg. Unsure of other advantages to diesel other than mentioned above. What do you Diesel guys run for fuel filters?? I am looking at an '05 2500 with the 5.9L. A buddy says it should be 2 micron fuel filter, if it's bigger than that I might expect to replace injectors fairly soon (around the 150,000 km range).