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50 to 1 gas oil mix calculator

Enter your fuel volume and ratio. The answer is in millilitres, because that is what the bottle is marked in.

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Oil to add—
    Follow your engine manufacturer first. Two-stroke mix ratios are specified by the engine manufacturer and vary between engines. Running too little oil causes rapid and permanent engine seizure; too much fouls plugs and clogs exhaust ports. Always use the ratio in your equipment's manual over any general figure, use oil meeting the specification the manufacturer names, and mix fresh — petrol with ethanol degrades in storage.

    How much oil per litre at 50 to 1?

    20 millilitres of two-stroke oil per litre of petrol. A 5 litre jerry can therefore needs 100 mL, and a 20 litre drum needs 400 mL. At 40:1 it is 25 mL per litre, and at 32:1 it is 31 mL per litre.

    Why the metric default matters here

    Almost every two-stroke mixing chart online is built around US gallons and fluid ounces. Canadian fuel is sold in litres, and two-stroke oil is sold in millilitre bottles.

    Converting a US-gallon chart in your head at a petrol station is how people end up guessing, and guessing on a fuel mix is how engines get destroyed. This calculator works in litres and millilitres first and offers gallons as the secondary option.

    Note also that a US gallon and an Imperial gallon differ by about 20%. Older Canadian equipment manuals sometimes specify Imperial gallons, which makes a US-gallon chart wrong by a fifth.

    The formula

    The ratio is fuel to oil, so a bigger number means less oil.

    • oil (mL) = fuel (litres) × 1000 ÷ ratio
    • 50:1 → 20 mL per litre → 100 mL per 5 L
    • 40:1 → 25 mL per litre → 125 mL per 5 L
    • 32:1 → 31.25 mL per litre → 156 mL per 5 L
    • 25:1 → 40 mL per litre → 200 mL per 5 L

    Getting the direction wrong is the dangerous error. A 50:1 mix contains less oil than a 25:1 mix, not more. Running a 25:1 engine on 50:1 fuel starves it of lubrication and can seize it within minutes.

    The ratio is set by the engine, not by the oil. Check the figure stamped on the housing or in the manual — modern equipment is usually 50:1, older two-strokes often 32:1 or 25:1.

    Worked example: a 5 litre can at 50:1

    You are filling a 5 litre jerry can for a chainsaw specified at 50:1.

    1. Fuel volume5 L
    2. 5 × 10005,000 mL
    3. Divide by 50100 mL
    4. Total mixed volume5.1 L

    100 mL of two-stroke oil into 5 litres of petrol.

    Most two-stroke oil bottles have a measuring chamber marked at exactly this quantity, because 100 mL per 5 L is by far the most common mix in the domestic market.

    Mixing practice

    • Pour the oil into the empty can first, then add fuel — it mixes far better that way
    • Use fresh petrol; mixed fuel degrades within about 30 days
    • Never mix in the machine's own tank
    • Use oil rated for air-cooled two-strokes, not outboard or automotive oil
    • Shake before every refill, since the mixture can separate on standing
    • Label the can with the ratio — two cans at different ratios look identical

    Common questions

    How much oil for 5 litres at 50 to 1?

    100 millilitres. The calculation is 5 litres times 1,000 millilitres, divided by 50. This is the most common domestic mix, and most oil bottles have a measuring chamber marked at exactly 100 mL.

    What happens if I use too little oil?

    The engine loses lubrication and can seize, often permanently and often quickly. Running a 25:1 engine on a 50:1 mix is the classic version of this error. Too much oil is much less dangerous — it fouls plugs and smokes, but rarely destroys anything.

    Is 50:1 more or less oil than 32:1?

    Less. The ratio is parts of fuel to one part oil, so a higher first number means the oil is more diluted. 50:1 is 20 mL per litre; 32:1 is about 31 mL per litre.

    Can I use car engine oil?

    No. Two-stroke engines burn their oil along with the fuel, and need oil formulated to combust cleanly in an air-cooled engine. Automotive oil leaves deposits that foul the plug and the exhaust port.

    How long does mixed fuel last?

    Around 30 days before it starts to degrade, and less in hot weather or with ethanol-blended petrol. Mix what you will use, and drain equipment before long storage.

    Where these numbers come from

    Last verified 2026-08-01 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.

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