I’ve just come across this really interesting site and they have a whole range of them.
“Obviously” it’s illegal in a certified aircraft but presumably they will work just fine? One issue might be fuel system compatibility (seals, etc).
With Avgas 100LL having a full rich octane rating of 120 I see little need for them.
The octane number gives resistance to detonation measure, is not related with other performance figures. As A_and_C says, there is no benefit using “boosters” in the usual juice used in GA. Maybe in Africa, to treat some unknown barrels.
I used to have that stuff back when I flew the SR20 to certain places in Eastern Europe, figuring that I would add it when topping up the fuel tanks with auto fuel. But then, I figured that it might just do harm and that my non-turbo engine wouldn’t be the slightest bit affected by some lower octane in the cruise flight phase, so I never used any of this.
I think the Reno racers use over 160 octane, plus other stuff, still technically GA
What I was getting at was whether e.g. owners of turbocharged engines, none of which have been certified (by Lyco) for 91UL, could just unofficially put this stuff in if fuelling with 91UL or with unleaded car petrol.
It isn’t expensive.