Middling engine performance, overheating, and coolant loss would typically go hand-in-hand when dealing with a blown head gasket, but it all depends on the point of failure on the seal.

Permanently fixes blown Head gaskets, cracked heads and porous engine block One bottle is enough to Fix gaskets in cars, SUVs and small trucks; large engines Require two bottles The ceramic micro ...

The gasket in question is probably the head gasket and when this fails, it can allow the engine oil and coolant to mix, which is why you’re seeing oil in the coolant expansion tank. If you check the ...