Gas Oil Ratio Calculator (2-Stroke)
Calculate 2-stroke oil and gas mix for any ratio: 50:1, 40:1, 32:1, and 25:1.
For chainsaws, dirt bikes, outboard motors, and all 2-stroke engines.
2-Stroke Fuel Mixing: Why It Matters
Unlike 4-stroke engines, 2-stroke engines do not have a separate oil reservoir. The oil that lubricates the engine’s pistons, bearings, and cylinder walls must be mixed directly into the gasoline before it enters the engine. Getting the ratio wrong has serious consequences.
The Formula Oil Volume = Gas Volume ÷ Ratio
For example, at 50:1: for every 50 parts of gasoline, you add 1 part of 2-stroke oil.
- 1 US gallon of gas at 50:1 → add 2.56 oz (75.7 mL) of oil
- 1 liter of gas at 50:1 → add 20 mL of oil
Common Ratios and When to Use Them Different engines require different ratios. Always check your owner’s manual. When in doubt, use a slightly richer mix (lower ratio number) rather than leaner, because running too little oil will destroy the engine.
- 50:1: Most modern 2-stroke equipment (chainsaws, string trimmers, leaf blowers, many dirt bikes, outboard motors). This is the most common ratio today.
- 40:1: Common on older equipment and some dirt bikes. Also used as a safe general-purpose ratio.
- 32:1: High-stress or older engines. Snowmobiles from the 1990s. Some Yamaha and Polaris outboards.
- 25:1: Very old or high-wear engines. Also recommended by many manufacturers during engine break-in.
- 16:1: Very old engines from the 1950s–1970s era.
What Happens With Wrong Mix Ratios Too much oil (rich mix): excessive smoke from the exhaust, fouled spark plugs, carbon buildup in the exhaust port, reduced power, oily residue. Too little oil (lean mix): insufficient lubrication, overheating, piston seizure, permanent engine damage — often within minutes of operation.
Always Use Quality 2-Stroke Oil Use oils rated JASO FD, ISO-L-EGD, or API TC. Avoid substituting with motor oil, gear oil, or vegetable oil — these can damage seals and cause premature wear.