Best Fuel Additives to Increase Horsepower

Which additives genuinely add power, which only restore power you already lost, and the one condition that decides whether an octane booster does anything at all. US & Canada, 2026.

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“Increase horsepower” gets used loosely in this category, and it covers two genuinely different products that work through different mechanisms. One kind restores power an engine already lost to deposits. The other kind can, under specific conditions, unlock power the engine never had. Confusing the two is how people end up disappointed.

Last updated 2026. Reviewed against dyno testing discussions of octane boosters and AMSOIL’s current product documentation.

On This Page

1. Quick answer
2. The mechanism most guides skip: “knock-limited” is the only thing that matters
3. Two different jobs, two different additives
4. The “10-point boost” marketing trick
5. Which one fits your vehicle
6. Alan’s take
7. Frequently asked questions

Quick Answer

If your engine is stock and already running its recommended octane, an octane booster will not add horsepower, because the factory tune isn’t holding back timing it could otherwise use. If your engine is tuned, turbocharged, supercharged, high-compression, or currently forced to run lower octane than it wants, a real octane booster like AMSOIL DOMINATOR Octane Boost can let the ECU add timing and genuinely make more power. Separately, a PEA-based cleaner like AMSOIL P.i. doesn’t add power beyond spec, it restores power an engine already lost to injector and combustion chamber deposits, AMSOIL’s own third-party testing showed up to 14% horsepower restored on a deposit-fouled GDI truck.

Important legal note: AMSOIL DOMINATOR Octane Boost is positioned for off-road and racing use, not for street-driven, emissions-controlled vehicles. For a legal street or powersports application, AMSOIL’s Motorcycle Octane Boost is the product built for that use.

The Mechanism Most Guides Skip

“Knock-Limited” Is the Only Thing That Matters

Octane doesn’t measure energy content and it isn’t a source of power by itself. It measures a fuel’s resistance to knock, the uncontrolled early ignition that happens when cylinder pressure and heat get ahead of the spark. Higher octane fuel simply tolerates more ignition timing advance, or more boost pressure, before that happens.

That single fact is why an octane booster helps some engines and does nothing for others. A modern engine’s computer uses a knock sensor to add ignition timing until it hears the first sign of knock, then backs off. If your engine is already running the octane its factory tune was calibrated for, the ECU has already found that limit, and pouring in more octane doesn’t give it anywhere further to go. Real-world dyno testing on stock, non-turbo, non-tuned engines consistently shows this: no meaningful gain, because the engine was never being held back by fuel.

The engines that do respond are the ones that are “knock-limited,” meaning something about the setup, a turbo or supercharger, a high compression ratio, an aggressive tune, or simply running lower octane than the engine wants, is forcing the computer to pull timing to avoid knock. Take that limitation away with a real octane increase, and the same computer can add the timing back in and make more power. One documented dyno test on a turbocharged, mildly modified car showed a real gain, several horsepower with a modest octane increase, and more with a larger one, specifically because the car was knock-limited on its baseline fuel and the tuner could add timing as octane went up.

Restoring vs. Unlocking

Two Different Jobs, Two Different Additives

Notice these solve opposite problems. A cleaner brings a deposit-fouled engine back up to its original spec. A booster can push a knock-limited engine past its factory spec. Buying a cleaner expecting it to add power beyond what the engine was designed for won’t work, that’s not the mechanism. Buying a booster for a stock, healthy engine that’s already running its recommended fuel won’t do much either, because there’s no knock limit for it to remove.

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Read the Fine Print

The “10-Point Boost” Marketing Trick

Plenty of bottles on the shelf advertise a “10-point octane increase” or similar. That language is often technically true and practically misleading, because octane is commonly measured in whole numbers, but marketing sometimes counts in tenths. A “10-point” increase can mean 1.0 full octane number, not 10 full numbers, which is a meaningful difference when you’re deciding whether a product is worth buying.

AMSOIL states DOMINATOR Octane Boost raises octane up to four full numbers, dosed at one 12 oz. bottle per 15 gallons, which is a specific, checkable claim rather than a vague “points” figure. Whatever product you’re comparing it against, look for a stated number of full octane points and a stated treat ratio, not just the word “boost” on the label.

Matching the Product to the Vehicle

Which One Fits Your Vehicle

If you’re not sure whether deposits or a fuel limitation are behind lost power, start with the cleaner. It’s the cheaper test, it never hurts a healthy engine, and our guide on whether injector cleaner actually works covers the honest limits of what it can and can’t fix.

Alan’s Take

Frequently Asked Questions

Real Power, Restored or Unlocked

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