What does an octane booster do and when do you need it? Depending on the type of engine you have, pumping the kind of gas with the appropriate octane level is critical.
If you have a car, or have driven a car, or have ridden in a car, or have basically had any interaction with a car, you’ve seen these places called gas stations, or fill stations, or petrol stations, if you like. If you’ve seen these, you’ve seen three separate prices, corresponding to some double-digit numbers that correspond to words that say “regular unleaded” or “super unleaded” etc, where the number 87 corresponds to regular unleaded. Those numbers are called octane ratings. Like it or not these numbers actually mean something, and depending on what kind of car you have, can be extremely important to pay attention to. If you have a Mercedes and you’ve been filling it with 87 octane, you could be destroying your engine.
The numbers 87, 89, and 91 above the fuel pump you’re about to use denote that the pump is going to give you gasoline that is 87, 89, or 91% octane. Simply put, the numbers are the stability of the gasoline. If you use 87 when you should be using 91, your engine could knock, where fuel burns too early when compressed. Each engine is tuned to use a specific kind of gasoline, so unfortunately just shoving 91 into every vehicle under the sun won’t really improve anything in terms of performance. In order to know what kind of octane you should be using, check your owner’s manual.
An octane booster is an assortment of chemicals designed to lower the risk of knock, so adding it to your fuel is going to make a difference but not in the way it would appear. Using Octane booster is more of a preventative measure, where if you accidentally put lower octane than you should, you can add a bottle of octane booster to raise the octane level for that tank of gas. The idea behind this is not to replace higher octane but to use in an emergency. Depending on which brand you get, the active ingredients may vary. Since the only thing that can effectively raise octane enough to see a difference is lead, which is no longer road legal, other chemicals are used like MMT and Ferrocene. Some people also use Ethanol in order to boost octane, but it will make your engine burn leaner. If you plan to run ethanol, be sure to have your car tuned for it.
An engine that uses high octane typically needs it because of how high their compression ratio is. A BMW engine, for example the N54 which was present in the 3 Series starting in 2006, has a compression ratio of 10.2:1, which is pretty high. That means the compression stroke is longer than other engines with lower compression ratios, which means the octane used needs to have a higher tolerance. Therefore putting in 91 octane would work best for how the engine is made and tuned. Similarly in a car with lower compression, like a 1995 Mustang GT which has 8.5:1 compression, would use lower octane because the compression stroke is shorter, so it needs a fuel with lower compression tolerance.
If we had to give a recommendation which what octane booster to get, we’d go with Royal Purple. In terms of product history, they have proven time and time again that their products work for the better. When it comes to gear oil they're hard to beat. Lucas Oil has come highly recommended by other websites, but when it comes down to it, it just depends on which booster is best for your particular engine.
Really though, no matter what engine you have the best thing is to have it tuned for higher octanes, instead of using octane boosters. It’s the proper way of doing things.