Recieved a hand me down Generac 5500/6500 prtable gasoline generator. It has a 10hp B&S engine with splash lubrication. I actually have two questions, I can not find any info on Oil for it, 30 weight? or something different?. It smokes moderately (oil bypassing rings, as spark plug is oil coated as well). Is there anything to do for the smoking condition?