Reply to "General question about oil..."

As I understand it, oil change recommendations vary by vehicle. Over time, the oil becomes acidic as a by-product of the combustion process which create a mild acid that actually etches away internal engine surfaces at the micro structure level, which over time increases componant tolerances. On my Acura, I change the oil once a year, and even then it is light brown. But my Pantera with it's "old school" tolerances (blow by) the oil that was fresh in June is black by September, so it gets changed far more often.