Question: how much does stp octane booster increase octane?
Answer: STP Octane Booster Claiming to increase the octane 2-5 points, in a well-designed-for-pouring bottle, the STP - used in the ratio determined by the label - improved the octane marginally by just over half a point. A little disappointing unless you interpret STP's claim actually meant 0.2-0.5 points.