Oh, so paint thinner and mineral spirits are the same thing? Then what is solvent? From the smell of the can I bought it smells like mineral spirits and the can says it has naptha. There sure seem to be a lot of names for the same stuff.

My pump says, if mineral spirits are used the pump may not last as long. But it doesn't say not to use it.

Either way the $30 I spent on this 5 gallon can of solvent from Napa seems like a ripoff. I guess from what you say I will just take the empty can to the paint store and have it refilled with paint thinner. This should be around $1 per gallon I would expect. I still thought mineral spirits and paint thinner were not quite the same, but what do I know.

P.S. Will the stuff also harm the rubber of my valve seals? I plan to clean my head today and am not planning to disassemble the valves. It looks to me like this head is fresh.

54 3100 with 235
62 flatbed dump C60 with 261