I think if you are going to push it longer, it is much better to have a synthetic. Pennzoil turns to a thick sludge when it is old. Ramius lost an engine in a newer truck because of it. He rarely drove it, so it sat longer than the recommended time, but not the mileage. His engine seized and was ruined. The oil that came out of it looked like gloppy jam. The synthetics don't do that. No more Pennzoil.
Yeah, I think I'll be driving a lot less once I get to Ft Collins, so I need something that will last for a while. So I'll just have an oil fund. Next to my Christmas fund, my semester fees fund, and my anime fund. (I'm planning to have really precise excel spreadsheet budgets, rather than little envelopes full of cash!)