"Jose" wrote

I'im hardly an expert, but I've been told by our mechanic that another
thing that happens is that the carbon chains that make up the oil break.
It's still oil, but now it has shorter chains and different properties,
and eventually doesn't do very well at what it's supposed to do.

True, but I think the shorter chains also evaporate more readily. There
must be some way to deal with that, because I know that some large engines
never have their oil changed. It blows my mind.
--
Jim in NC