Whats your timing set at? If its at 14 or higher, then i'd seriously think about upgrading to 92-up gas.
I'd suggest using a 15w40 senthetic blend.
the 10w30 or 20w50 or whatever is the weight of the oil, basically the thickness.
The viscosity of the oil is basically how slippery it is (the friction coefficient sorta)

sorry about all the basically's and sorta's