Free calculator
Gas-Oil Mix Calculator for 2-Stroke RC Engines
How much 2-stroke oil to add to the gas for your 1/5 scale RC car, based on the ratio your engine calls for.
What it’s for
1/5 scale RC cars usually run two-stroke gasoline engines, like the ones on a string trimmer. These engines are lubricated by the oil mixed into the gas, so the ratio has to be right: with too little oil the engine can seize, and with too much it fouls the spark plug and smokes more.
How to use the calculator
- Enter the amount of gas you’re going to mix, in US gallons or liters.
- Choose the ratio your manufacturer gives (for example, 25:1 means 25 parts gas to 1 part oil).
- The calculator tells you the fluid ounces of oil to add, with milliliters in brackets, and the total volume of the mix.
Quick chart (oil per gallon of gas)
| Ratio | Oil per US gallon | Oil per liter |
|---|---|---|
| 20:1 | 6.4 fl oz (189 ml) | 50 ml |
| 25:1 | 5.1 fl oz (151 ml) | 40 ml |
| 32:1 | 4 fl oz (118 ml) | 31.3 ml |
| 40:1 | 3.2 fl oz (95 ml) | 25 ml |
| 50:1 | 2.6 fl oz (76 ml) | 20 ml |
Tips for mixing fuel
- Use good-quality 2-stroke oil and an approved fuel can.
- Pour in part of the gas first, then the oil, then the rest of the gas, and shake well before each use.
- Measure the oil with a measuring cup or a syringe, not by eye.
- Only mix what you’ll use within a few weeks: the mix loses quality over time.
You can find 2-stroke oil and fuel mixing bottles on Amazon.
Torn between gas and nitro? Read the guide to nitro and gas RC cars.
Frequently asked questions
How much oil goes in a gallon of gas at 25:1?
About 5.1 fl oz (151 ml). Divide the gas in fluid ounces by the ratio: a US gallon is 128 fl oz, so 128 ÷ 25 = 5.12 fl oz of oil.
What mix ratio should I use in my gas RC car?
The one your engine or oil manufacturer recommends. During the break-in of a new engine, some manufacturers recommend a slightly richer oil mix: always check their manual.
Does it work for a nitro RC car?
No. Nitro engines run on a dedicated, premixed glow fuel made of methanol, nitromethane and oil, and you don't mix it at home.
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