Sta-Bil is good, but I think the iso-heet is what is doing you the most good. Sta-bil will only keep the fuel stable over a period of time. Keeps the additives in the fuel in suspension. The iso-heet helps keep the water out and water seems to be the biggest problem. something else I have found out and told my customers is: DO NOT buy their gas at small country stations if they can help it. Most bikes run premium fuel (92 octane) and the little country stations do not sell enough of that to keep the moister out of their tanks. keep a small bottle of octane booster in you saddlebags and if you absolutely have to buy fuel at a small country station, buy regular (83 octane) and add some octane booster to it.
I had one customer, an over the road truck driver that brought his Sportster in 3 times one summer. Each time the carb was plugged and the float bowl contained a milky goo. Turns out he was filling his bike with premium at a little station close to his house ( in rural Mississippi)before he left on a trip. Each time I cleaned the carb and the bike ran well. After I told him about the “little country stations” I did not see him until he needed tires. So I kinda figure the same applies to a car.
My 2002 RK Classic with a 95”er, (not carb, darn), would hardly run on that crap when I got stuck buying a tank of it on a cross country run.
It was gutless and it ran hot as hell. I didn’t have any additives with me, but if I were to set out on another long trip, I would certainly carry the stuff.
I only had a thousand miles on the synthetic oil, but I changed it that night, changed the spark plugs, filled with good high test and all was good again.
I put on over 9000 miles on that month long trip, and that was the only gas I had trouble with.