How to Mix 2-Stroke Fuel: The Complete Guide

Mixing 2-stroke fuel (also called 2-cycle or two-stroke premix) just means adding the right amount of oil to your gas so the engine gets lubricated as it runs. Get the ratio right and your chainsaw, trimmer, or dirt bike runs clean for years. Get it wrong and you risk a seized engine or a fouled plug.

The one rule: oil = gas ÷ ratio

Every 2-stroke ratio is written as gas:oil — so 50:1 means 50 parts gas to 1 part oil. To find the oil for any amount of gas, divide:

• 50:1 → 2.56 oz of oil per US gallon (20 ml per litre)
• 40:1 → 3.2 oz per gallon (25 ml per litre)
• 32:1 → 4 oz per gallon (31.25 ml per litre)

Use the calculator to get the exact amount for your gas can — switch between gallons and litres, and pick your ratio:

Fuel → oil / Oil → fuel

Fuel → oil Oil → fuel

Amount of fuel

Gallons (US) Litres

Equipment (optional) Choose equipment… Chainsaw (50:1) String trimmer / weed eater (50:1) Leaf blower (50:1) 2-stroke lawn mower (50:1) Dirt bike / motorcycle (40:1) Outboard motor (50:1)

Mix ratio

100:1 50:1 40:1 32:1 25:1 20:1

Custom ratio (X : 1)

Calculate Reset Copy link to this mix

Add this much oil

12.8 oz

≈ 378.54 ml

Add 12.8 oz of 2-stroke oil to 5 gal of gas at a 50:1 ratio.

Step by step

1. Find your ratio. Check the engine’s fuel cap, the owner’s manual, or the oil bottle. When in doubt, the richer ratio (more oil, e.g. 40:1 over 50:1) is the safer guess.
2. Use fresh gas. 87+ octane, ethanol-free if you can get it. Stale or high-ethanol fuel is the #1 cause of small-engine trouble.
3. Use a real 2-stroke oil — never regular motor oil. Match the spec your engine calls for (e.g. JASO FD for air-cooled, TC-W3 for outboards).
4. Measure the oil for your gas amount (see the calculator above) into the empty, approved fuel can.
5. Add the gas, then shake the sealed can to combine before filling the tank.

Don’t guess the oil

Too little oil removes the lubrication film and can seize the piston. Too much oil makes it run rich — heavy smoke, a fouled spark plug, and carbon buildup. A little extra is far safer than too little, but measuring for your exact ratio is best.

Need the full reference tables? See the 50:1, 40:1, and 32:1 pages, the printable mix charts, or the 2-stroke mix chart guide, which puts every ratio in gallons and litres in one place. For specific equipment, see the chainsaw and dirt bike guides. Not sure which oil rating your engine needs? Read TC-W3 vs JASO FD.