So, I realized earlier while looking at a quart of emergency oil I had that it was rated API SF, meaning not recommended for cars newer than 1988. I would assume this oil had quite a bit more zinc and would protect the cam better, but I don't know how much worse it would sludge the engine up. So you know, it's Dollar General brand 10w40.

Im currently running royal purple 15w40 and will be using it every third change with Rotella on the other two just to keep things clean, but I'm curious what would happen if I were to use this API SF oil regularly since these engines are of quite an old design?

Thanks guys!