Dont think either of those received FBHVC endorsement as their list only shows Millers, Red lIne, Castrol and Tetra Boost. On longer high speed runs I use Millers lead/octane booster with 95 fuel in my Vitesse 2L as it runs better. Also I hope it protects my valves as they have been reground and I believe, for a period, suffered quite severe valve seat recession although this was probably due to running a weak mixture due to air leaks which have now been cured....