I'm going to hit 300k miles next month. Here are my thoughts:
1) I use Mobil-1 high mileage, changed every 5k. AC Delco PF-52 filter.
2) Occasionally (every 50k miles or so) I use an engine oil flush when I change oil.
3) I avoid knock like the plague - I listen for it an increase my octane if required. Knock hammers the crap outta your bearings.
4) Stay on top of your antifreeze too- change it every few years. And I assume everyone has installed metal intake gaskets by now. I'm in the minority and still use Propylene Glycol.
5) Don't bother with fuel injector cleaner.
Other than that - just keep driving. Your mileage may vary.
-Bob C.
