Haven't heard of this stuff in a long time. Back in the 60's and 70's we used to use Anti-Detonation Injection (ADI) or water/methanol injection in turbocharged aircraft engines. It always worked good and allowed for more timing and cooler combustion temperatures than without. It was mainly used on takeoffs too, not at cruise. I had easy access to the "watered down milky looking stuff", so I installed a system in my truck and camper setup. The systems for automobiles back then were really crude (vacuum controlled), but hopefully they're better today. The biggest problem was when activated (higher engine loads) I could go through a gallon of it pretty fast.....like in mountain driving and such. On board storage (in a vehicle) of enough of the mix for a whole trip was the other big problem. I eventually gave up on it because I felt the it wasn't worth the effort for the slight gains.
IMO, using it in a newer, normally aspirated computer controlled vehicle today would, for sure, further reduce these slight gains. I will say though, that if you're using forced induction of some sort, it very well may be worth giving it a "shot" (literally) though.