Octane Boosters and the Truth Behind Them
Octane numbers are something we see every day and probably take for granted. We all know this is a rating means of measuring a fuel’s resistance to pre-ignition, but how does that apply in a practical sense? Let’s first assume you have a car that runs fine on 91 octane. What could you gain by changing the fuel you refuel with? Going down to 87 octane will give you better mileage, but could risk detonation depending on your car’s engine. By going up to 93 octane, you can allow your car to run over time by gaining horsepower. Due to the lower BTUs per gallon, you will give up some miles per gallon. So right away you can see that it’s a balancing act.
Taking a closer look at this, you’ll notice that the extra power comes from the car’s ability to move ahead of time and not the fuel itself. Higher octane fuel has fewer BTUs, but still generates net power due to the timing advance and the higher boost it can achieve. In modern vehicles with knock sensors, the timing varies constantly to achieve the best balance between performance and economy. Because this adjustment takes time, simply switching to a higher octane on the track is not enough. Fuel needs to run ahead of time to allow the car to make up for it. So using 91 all the time and then going to the track and filling with 95 is not going to help your track times. However, you will have a faster car on the way home.
The other end of the spectrum is less octane. The downside here is the risk of preignition and high EGTS. Both can lead to melted or bent pistons. The valves and the head are also put at risk. If you have a modern vehicle, it will detect it and delay time to prevent damage. This timing modification is easy to detect with an OBDII scanner and it is easy to diagnose too much fuel with too little octane.
Due to the above reasons, many people turn to thrusters as a way to get good fuel and perform well on the track. The problem with them is that most of them don’t work. If you find one that works, adding it to your tank a day before you hit the track can be beneficial. Despite the benefit, use boosters sparingly as most rely on MMT as a means of increasing octane. Excessive MMT can cause problems with sensors, injectors, or even the exhaust.
By now, you’re probably confused again by what this all means. In short, if your car has no compression changes, raised RPM limiter, or a lot of boost, you should probably use whatever fuel the dealer recommends. If you have an engine built for racing, stick to a racing fuel that meets the needs of your engine. If you have a slightly tuned engine and enjoy the occasional track day, add a bottle of octane booster the day before and call it a day. Don’t rely on backup all the time.