Fuel Additive Calculator

Work out how much ethanol or toluene to put in your tank. See the blend's octane, its cost and its effect on your acceleration times in one place. Works offline.

Fuel Additive works out how much additive to put into the gasoline in your tank. No formulas to juggle — you get the right ratio in seconds. You can also track the octane of the blend, what it costs you, and what it actually does in your own runs.

CALCULATE — WORKS BOTH WAYS

By amount: You have 5 litres of ethanol and you want to know what it will do. Drag the amount and watch the resulting ratio and octane update live.

By target: You want an E30 blend. Pick the target and it tells you how many litres to add.

Additives: ethanol (RON 109), toluene (RON 121), or a custom additive whose octane you enter yourself. Base gasoline octane is chosen from 93, 95, 98 and 100.

BLEND OCTANE

The octane of your base gasoline, the additive already in the tank and the one you are adding are all taken into account. You see the estimated RON of the blend and how many points it gained.

COST

Enter the price per litre of gasoline and additive, and the app works out what the additive costs you, the price per litre of the resulting blend, and — most usefully — the cost of every RON point you gain. Whether ethanol or toluene is the economical choice at your prices becomes obvious.

GARAGE

Save your vehicles: tank capacity, the additive already in the tank and the fuel grade you run. Selecting a vehicle fills everything in and warns you if the blend would overflow the tank. Your fuel prices live here too.

RUNS

Log your 0-100, 100-200 and 402 m times. Note which blend you used, the road gradient and the conditions. The app sorts the times and shows the gap to your personal best, so you can see what different blends really do in your own car.

The reference tab holds our own measurements.

INFO

A short section on why high octane produces power, ethanol's charge-cooling effect, and which engines should not expect a gain.

ALSO

• Turkish, English and Spanish
• Fully offline — no internet needed
• No data collected, nothing sent to any server
• Set values with sliders or tap the number and type it

SAFETY NOTICE

Results are estimates — verify them yourself before mixing. Blending additives may void your vehicle's warranty and can breach emissions and fuel regulations; check your local rules. High ratios damage seals and fuel lines. High ethanol ratios can damage the fuel system of vehicles that are not equipped for them.

Only run acceleration tests on a closed track or private land closed to traffic. The app has no timer — you enter the times yourself.

You use this app entirely at your own risk.

Octane is calculated with a linear volumetric blend. In reality ethanol's blending octane is not linear and contributes more than expected at low ratios, so the true value is usually a little above this estimate.