When I was considering rebuilding my Metro's engine, I was going to use thermal coatings and dry film lubricants to increase thermal efficiency and reduce pumping losses.
I was planning on using this kit:
PEK1 Engine Kit - Assembly Lubricants
With it you can coat tons of stuff. The thermal coating can go on the piston tops, combustion chamber, and valve bottoms. The dry film lube can go on main bearings, cam journals, valve shafts, piston skirts, all to reduce friction. I have no idea how well any of it works, but it sounded good.