Originally Posted by Red90
Then why not use a multi weight like a 0W20?
Because even the "0" in 0/20 is not as thin as ATF if your engine runs good with ATF I suspect due to inevitable tolerances in carbs.
That aside marvel mystery oil is better than both for that application! It has the correct consistency and will keep the carbs clean & clean out your valves to boot! Additionally and more importantly its not affected by temp changes!