What about fulfilling the warranty requirements? How do you keep up the records if you do it yourself?
It would be prety difficult for a dealership to prove that any kind of warranty issue is related to engine oil - be it age or lack thereof.
Per the Manuson-Moss Warranty Act: "The federal minimum standards for full warranties are waived if the warrantor can show that the problem associated with a warranted consumer product was caused by damage while in the possession of the consumer, or by unreasonable use, including a failure to provide reasonable and necessary maintenance."
So I mean if the engine is seized and the oil pan is bone dry, you might be screwed. Also if the oil pan is full of sand or the oil comes out in chunks, you might be screwed... Other than that, it's really kinda hard for the dealership to win that argument, and I know 'cause I've been on the dealership side... We once had a 3.0 Taurus with "blue metal" inside the cylinders - obviously a result of overheating due to what we suspected was "rampant abuse of a rental vehicle" (which the car was.) However, for all the trouble it'd have taken to fight it, it was simply easier to throw a new block at it and move on to the next vehicle.