My Slant seems a little ill

Not all head gasket leaks intermix fluids Bill, you know that me thinks.:D
Some leak compression into oil, and some into the waterjacket, and some can miss both and come right out the side of the head. (Rare but happens)

That's a good call on the small leak, and a cooling system pressure test will help with that. (pump it up and look it over good)
85,000 ? Could be a head gasket. A pressure test with it running can find that by pumping the system up to pressure (say 12 lbs), note the pressure carefully and rev it up good a few times.
Is the pressure higher?

His prime symtom is overheating from coolant loss, be it coolant loss then overheat, or overheat and then coolant loss.
They are hard to tell sometimes, but the pressure testing can tell you which one it is.

Start with the easy obvious stuff first though for sure. (The possibility of a small leak)