Well, on my current car...
The turbo seals were leaking a lot of oil which was being burned out the exhaust... Up to a point where the car was bruning 1 litre every week (~ 1 quart). My engine doesn't like being ran even a little low on oil, so I ended up spinning a bearing and getting a nasty rod knock.
No big deal, order used engine from Japan, turn up the boost a bit more.
Keep driving for months and months, stop caring about oil changes as this engine is toast anyway, keep adding small mods here and there, racing car, etc... Now running even more boost, car should be making around 90hp more than stock (320 versus 230), and one night on a good highway run something breaks... BANG, rattlerattlerattle, yay.
Spend the next month preparing the new engine I had bought and dropping it in, with a few more mods even.
Couple of months later blow the head gasket. And that's where I am now. This week I'll be pulling the head, which on my car is almost as involved as pulling the whole engine.
