Brian,


EPA is a compound, specifically zinc dithiophosphate, added to some special lubricants, like camshaft assembly lube, to prevent scuffing and galling between parts, until they wear in, as is the case between a camshaft and its lifters.

There is no real need for this additive in model engines.

But if the lubricant prevents the glow plug from becoming tight on its seat, despite the low thread pitch, I would suspect the existence of this stuff in the fuel.