I have a Fox .74 ABC, a Fox .60 ringed, a SuperTigre .51 and a couple of others I've been flying since 1991 or 1992 using Davis ABC mix, I would never think of adding any lube to it and my engines are all still as good as new. The .51 is a little tired but I suspect that is from a lousy break in when I was new to rc engines, ringed ones in particular. The .51 has always been flown with a 12x6 three blade since conversion to Diesel.