"I have never been given bad information on this site and the post here referencing a tired Cummins is the first I've ever heard such a description about a Cummins. As I read on I noticed that nobody flamed the guy and demanded proof for what he said about his engine. "
Maybe I'm reading your post wrong, but do I detect a hint of disbelief that a Cummins could actually be tired? Perhaps a forum of enthusiasts isn't the best place to find reports of tired Cummins. Every time I go to the Cummins dealer for parts, I find many people with tired Cummins and many hints on things to watch for. Cracked early model heads are prominent for me to watch for. More than a few boat owners are complaining about their 375hp 5. 9 replacement engines having a lower performance level than the worn 300hp 5. 9's they replaced. The dealer stocks plenty of heads, injection pumps, and replacement piston kits. He also does a rather brisk overhaul business. This is not to say that the Cummins is a defective engine, but that it's still just an engine. Engines wear out, and the Cummins engine has no magical properties to prevent that. The main reason for a 5. 9 Cummins being so trouble-free in its Dodge application is that it is a very de-tuned 5. 9 (to protect the transmission) and is relatively unstressed. Pushing a fifty foot boat through the water or a motorhome up a mountain is a heck of a lot more stressful on the old engine originally bought from Onan than pushing a 7000 pound pickup down the road. That being said, tired or not, I expect my Cummins to give me at least another 100,000 miles. It's got to; I can't afford another new truck!