“..How much Seafoam per gallon of gas?...”
I use about one ounce/gallon for unmixed gas and two ounces for 2-stroke mixed gas. I also use non-ethanol gas for all my small engines and my outboard. Ethanol is the death knell to small engines IMHO.
I’ve also used the blue-colored, marine-grade StayBil for storing non-ethanol gas for longer storage as well.
I use ethanol free gas in my chainsaw. The riding mower seems fine with it but I do put Seafoam in it over the winter (and start it once a week).
Thanks!