I live in southern Missori where it would be 40-100 deg F during mowing season (generally 60-100). The Scag commercial mower is Honda 21 hp twin w/spinon filter. 1.8 qt capacity. Honda gives several weight oil choices 5-30, 10-30, 10-40, 30wt, 40wt. It looks like 10w-30 0r 10w-40 would work well. I keep the mower in the garage and occasionally have to gas it up and move if for whatever reason in the winter but would probably never be started below 32 deg F. Would 15w-40 be good also. I will be using 10w-30 in my vehicles soon but feel maybe 10w-40 or 15w-40 would be better choices for the mower. Also, would you run neutra or soy in the gas? Neutra in the oil? Thanks for the help, Gary.