Engine Coatings?
the best ones are not for friction reduction, but heat retention or to deter heat transfer. You can combine these with other treatments and really get good measurable results. You want to keep th heat out of the intake ports, out of the intake itself, out of the exh valve and port, away from the piston dome, and out of the valve springs. You can also cryo treat the block, crank, rods,and heads to help make them stronger. They really do work. And they really do cost...lol.