I wasn't sure on the interval stuff. Thanks for the clarification. I know with truck diesels we'd do a water filter every oil change. 20,000 seems like a lot, but then they are rated for total gallons passed through them and the big diesels use more fuel.
I know you can save money driving one, but I'm not sure if it's the 'answer' or what repair bills look like vs a gas engine. I do know injector pumps aren't cheap (not lift pump). IIRC buddy told me the VW ones ran about $3,000 to replace and he'd done about 20 of them (head tech at the local VW dealer).
But it's like everything, if you know what you're buying into you'll be fine; if you don't you might be in for a big surprise ... accidentally put gasoline in instead of diesel, run the tank dry and fuel lock the pump, etc. I just don't think the 'average' person knows enough about them, but should. Not saying the average person know shit about gasoline engines though, lol.