The best part about a well designed diesel engine is that you cruise at about 50%. And I really well built diesel engine with a nice heavy construction will run on the pins all day long. Heavier is better in diesel design--because it lets you run it harder for longer periods of time. This is my one complaint with engines like the Duramax or Powerstroke-- they are too light in my opinion to really get the sort of reliability you want in a highly tuned engine. My self I would stick to the Cummins engines the ones built for commercial applications mostly. Yes, they are heavier, but a little extra weight is a bonus in reliability. That is why I like the old 2-stroke Detroit Diesels so much pound for pound they are at least 1.25 to almost 2 times as heavy as say a Cat or Cummins of the same displacement. Then you have the bonus that every other stroke is a power stroke. So that is a plus. But for a Jeep application-- I think the medium duty 4BT or 6BT (maybe even the new ISB 6.7) would be really awesome to play with. Especially if you set it up for Biodiesel.

The Greener Meaner Bio-Diesel Bandit Jeep...