STP 78574 5.25 Oz Octane Booster, Pack of 4

I don’t know how good this is for truly adding octane. The benefits are negligible. I feel like it helps give a smoother engine, but doesn’t add much to performance. My mustang can take 87 octane but when used for performance driving need 93. If I use 89 octane and add the booster, it really doesn’t even come close to the performance of 93… even with 2 bottles at once. I like the product, I think it helps, but at the end of the day, if you need higher octane, just buy it at the pump.