I run with the same oil as for a car, and always buy those marked with "added adjectives for high performance at both high and low temperatures" (where low is defined as the lowest air temperature it will get in my area). To keep the engine cool i've installed a Naraku Blowingwheel, which sucks more air in and around the engine. I've also installed a 31000 volt ignition coil and an iridium spark plug, which lowers engine temperatures. Also getting the right fuel mixture 14:1 is lowering the temperature, even though a slightly lean mixture can give more power.