Man, that's the first time I've ever seen anyone besides myself mention Marvel Mystery Oil. Been using that in my vehicles for many many years. In the gas, and sometimes in the oil. I run 20W-50 in my V6 Ranger, but thin it down with MMO when winter comes around. That's only if oil change time hasn't come around yet.
Yea, I like too, I have a Toro lawn mower with a Briggs & Stratton engine. My Dad bought it when I was 10 years old (47 years ago). it would, (I should say I ) mowed a 1 Acre lot from March to October once a week.
Every season in the Fall, on the last mow M.M oil was poured down the carb until it shut down (flooded it). In the Spring, the blade was sharpened, fresh oil and Gas mixed with M.M was poured in the mower, sometimes a new spark plug and the thing would firer right up for another season.
My parents downsized (no lawn to cut) The same year I bought my House, and I was given the mower.I still follow the ritual. The Grass catcher bag is long gone, the “Choke / Run” throttle is busted and ZIP tied to the handle, I replaced the rope on the pull start twice.
My Wife hollars at me at the end of the season when I pour the MM oil down the carb.
“WHY DON’T YOU GET RID OF THAT DAMN THING, YOUR SMOKING OUT THE NEIGHBORHOOD!”…… I can’t,It still runs great!
I lost my Dad to liver Cancer 1 year ago (81 years old)…..And although I HATED it when I was a kid, when my Dad would come out of the House as I was mowing the grass, and motion with his two hands in a vertical Karate chop motion (this meant, keep the mower straight, overlap your cuts, don’t waver). I still think of him fondly every time I cut the grass, and of coarse every time I smell M.M. oil.
I use M.M oil when I store my “66” I rev up the engine and slowly pour some M.M. down the 4 barrels until I see smoke coming out the exhaust (or when my Wife comes out of the house and yells at me). I then put my hand over the carb (starving it for air) so it dies. Every Spring just like the lawnmower it will start right up once the gas makes it to the carb.