Premix Calculator

How the 2-stroke premix calculator works

A 2-stroke premix calculator does one job: it tells you exactly how much pre-mix oil to add to a given amount of fuel so the gas-to-oil ratio in your tank matches what your engine needs. Enter the fuel volume in litres or US gallons, pick a ratio (50:1, 40:1, 32:1, 60:1 or a custom value), and the calculator returns the oil amount in millilitres or fluid ounces. There is no rounding fudge, no guessing — just the same fuel/ratio math your engine builder relies on, exposed as a one-tap tool.

How to mix 2-stroke fuel correctly

1. Decide on the ratio your engine manual specifies. Most modern enduro 2-strokes use 50:1 or 60:1 with quality semi- or full-synthetic premix oil. Race motocross 2-strokes typically run richer (40:1 or 32:1).
2. Use the calculator above to convert your fuel can size into the exact oil amount. A 5 L can at 50:1 needs 100 ml of oil; the same can at 32:1 needs roughly 156 ml.
3. Pour the oil into the empty (or near-empty) jerry can first, then add the fuel on top. The fuel splashes the oil into suspension as it goes in, giving a fully blended mixture in seconds.
4. Cap the can and shake for 20–30 seconds. Properly mixed premix looks slightly tinted but clear — no streaks, no oily slick at the surface.
5. Burn through mixed fuel within 30 days. Premix separates and oxidises in storage and old mix is a documented cause of cold-seizure on the next ride.

Common 2-stroke mix ratios — what each one means

• 50:1 — 20 ml of oil per 1 L of fuel. The default for most modern enduro 2-strokes (KTM EXC, Husqvarna TE, GasGas EC) when run on a quality JASO FD / ISO-L-EGD premix oil.
• 60:1 — ≈17 ml per 1 L. Specified by KTM/Husqvarna/GasGas when running their factory Motorex Cross Power 2T. Cleaner exhaust, slightly less power-valve gunk, but only safe with a premium oil rated for it.
• 40:1 — 25 ml per 1 L. The traditional MX safety-margin ratio. Used by older 2-strokes, race-prepped engines, and anyone who would rather burn a tiny bit of extra oil than risk a cold seizure on a slow trail loop.
• 32:1 — ≈31 ml per 1 L. Yamaha YZ / YZ-X race ratio, also common in vintage and air-cooled 2-strokes. Smokes a little more — but Yamaha specs it, and the engines last.
• 25:1 / 16:1 — Niche territory. Vintage motocross, two-stroke karts, and break-in mixes for fresh top-ends. Don't use these on a modern enduro bike unless your engine builder asked for it.

Recommended 2-stroke oil ratios by bike

Always check the owner's manual — what follows is the typical factory specification riders actually run. Premium synthetic premix oils unlock the leaner ratios; basic mineral oils generally don't.

• KTM 250 / 300 EXC, EXC TPI, SX: 60:1 with Motorex Cross Power 2T, 50:1 with most other quality premix oils.
• Husqvarna TE 250i / 300i, TC 250: 60:1 with the factory oil, 50:1 with everything else.
• GasGas EC 250 / 300, MC 250: 60:1 with Motorex, 50:1 otherwise.
• Beta RR 250 / 300 2T, Xtrainer: 50:1 (Beta specifies a minimum of 50:1; safer to stay there).
• Sherco SE 250 / 300: 50:1.
• Yamaha YZ125 / YZ250 / YZ250X: 32:1 with Yamalube 2R / 2S race oil.
• Honda CR / older 2-stroke MX: 32:1 — the long-standing race ratio.
• Vintage and air-cooled 2-strokes (≤1985): 25:1 to 32:1, depending on the engine.

Premix vs. oil injection (TPI / autolube)

Modern fuel-injected 2-strokes like KTM EXC TPI, Husqvarna TE i, GasGas EC i and TBI models inject oil directly from a separate reservoir, so you fill the fuel tank with neat petrol and let the bike meter the oil. The premix calculator on this page is for carburetted 2-strokes, race bikes, and any TPI/i bike you have manually converted back to premix. If you do run an injected 2-stroke on premix as a backup (for example after an oil-pump failure), most owners run 80:1 or 100:1 because the engine was designed to see roughly that ratio at low/mid throttle.