[Barry_R]

The coating applied to piston skirts by OEMs is not teflon. Its a DuPont D10 graphite in a polymer base. And it works to resist skirt scuffing. Best if screen applied - spray applications tend to be more sacrificial and wear off quickly - still helps, just not as long.

Nitriding (or something similar) is a hardness treatment done to many if not all aftermarket and most OE crankshafts at the manufacturer. It is neither a coating, nor a gimmick. It's an accepted process at all levels.

A fair amount of the remaining coatings are marketing or sols as "insurance" without a quantifiable power/performance benefit.