roadsta is absolutly correct. Do not put any of this crap in your tank. Modern fuels don't need any help and even if there was a way to increase octane, our engines are tuned for max performance at the rated octane. The computer will not crank up the boost nor advance the spark to take advantage of the higher octane.
These engines (sixes and eights) have direct injection. This is a senstive, high pressure fuel delivery system with VERY expensive injectors the squirt atomized fuel directly into the combustion chamber nearly 60 times per second at redline. Anything that changes the fuel's chemistry, viscosity or simply isn't gasoline suspended in solution is a recipie for disaster. Check out the old test from 5th Gear below.