What gas additives have I used? Fuel power, Lucas UCL, 2 stroke oil, and MMO.
Fuel power and Lucas may indeed lube things, but with no perceptible feel difference.
The TCW3 2 stroke oil works well, but is not really a cleaner.
So MMO gets the nod. Cleaning, lubrication, and feel [mostly idle quality].
Gas mileage? tough to tell, because I haven't run straight fuel in a long time. But not much difference. MMO would come out on top by general feel -at least there was never a hit downwards.
Oil additives? Ha! In years past U-Name-It.
Really.
But I have come to use only engine oil now, because they are so good nowadays. And like I said, maybe some thick stuff like STP for someone's oil burner.
I know MMO cleans, but have not personally used it in oil for a long time - decades. Except for the unseen ring area, none of my engines have needed any cleaning otherwise - no sludge or lifter ticks.
Since I had it in my hand, and winter is here, I decided to give it a 1/2 shot [16ounces]in the crankcase.
Maybe it is causing less friction, or being simply thinner caused my fast results.
It is worth it so peruse the actual MMO website:
http://www.marvelmysteryoil.com/
Not to hijack my own thread, but I have interest in LubroMoly.
I have mixed feelings. Almost assuredly less friction, but at what cost? What are the downsides? So not yet.