If the lawnmower has two compartments one for gas and the other for the oil, then put gas in the gas and a 30w type oil in the oil compartment. Simple as that. If you have an engine with only one compartment then you'll need to check on the manufacturers suggestions which is usually 40:1 or something close.
30 wt
5w30
Sae 30w
SAE 10w30 full synthetic any major brand.
Any straight 30 weight should do.
10W30 can be used, but SAE30 is best. 10W30 can run a bit hot, in warmer climates.
SAE 10w30 all year round or SAE 30 if it is only used in the summer. Use 100% Synthetic oil in this air cooled engine.
electricity
"6.6 craftsman " is insufficient info. -If you expect a sensible answer, please describe it fully.
What kind of engine? lawnmower, car.
straight 30 or a 10w30
SAE 10w30 weight synthetic oil.