Maintaining a fleet of local transit busses on E450 chassis. I know about Powerstrokes. The 7.3 was a VERY reliable engine developed over many years from the old 6.9L Navistar V8. As emission controls were added, they were tacked on to the outside of the unit. LOTS of of small oil and coolant leaks. Ford complained to Navistar about all of the leaks, and when they designed the 6.0 they put all the stuff INSIDE the engine, but they still leaked, not onto the ground, but inside the engine where you have to tear the whole thing apart. We'd put about 250,000 miles on a bus in 4-5 years, with 100% of that inside of a 36 square mile city. Our 7.3's usually never came out of the chassis during their life. With the 6.0L, they began having issues around 100k and had to be removed to have all of the "extra" internal components serviced. I actually purchased a spare engine so we could have one on hand to swap in when one started giving us problems. After that generation of busses, we went to the V10 gas motors. The selling point of the diesel in the first place was reliability, and the 6.0L killed that. The modifications recommended to make them bulletproof are basically to get all of the emissions crap out of the engine. As a governmental agency, that option was not available to us. Be aware that all of those modifications violate EPA and other federal regulations, and if some governmental functionary decides to make an example of you, you'll be the next Jammie Thomas-Rasset (the Massachusetts grandmother that was fined $1.9 MILLION because her grandkids downloaded music on her internet connection without paying royalties).