Two percent, four percent, one part oil to twenty parts fuel... The two-stroke mix makes everyone hesitate at the jerrycan. Here are the usual ratios in one table, the mistakes to avoid, and the golden rule: your engine manufacturer's ratio always wins.
Usual two-stroke mixing ratios
| Ratio | Oil per litre | For 5 L | For 10 L |
|---|---|---|---|
| 2 % (1:50) | 20 ml | 100 ml | 200 ml |
| 2.5% (1:40) | 25 ml | 125 ml | 250 ml |
| 3 % (1:33) | 30 ml | 150 ml | 300 ml |
| 4 % (1:25) | 40 ml | 200 ml | 400 ml |
| 5 % (1:20) | 50 ml | 250 ml | 500 ml |
The 5% (1:20) ratio is mostly found on older engines; most recent garden machinery engines run between 2% and 4% with modern oils. When in doubt, your machine's manual decides.
Why oil in the fuel?
A two-stroke engine has no oil sump: piston, cylinder and crankshaft lubrication relies entirely on the oil mixed into the fuel. Each intake stroke lubricates the moving parts before combustion. Without oil the engine seizes within minutes, which is also why a two-stroke must never run on pure petrol.
The mistakes that cost an engine
A lean mix (not enough oil) is the most dangerous: overheating, scuffing, piston seizure. A rich mix fouls the spark plug and produces smoke and carbon, but rarely kills the engine. Another trap: aged mix. Petrol goes stale and oil separates; beyond a month, prepare a fresh mix and always shake the jerrycan before filling.
Finally, measuring by eye with a bottle cap remains the first cause of wrong ratios: on 5 litres of fuel, a 30 ml error is enough to turn a correct 4% into a lean mix.
The right tool: a graduated measuring cup
A dual graduation measuring cup removes all maths: read litres of fuel on one side, millilitres of oil on the other, pour, mix. Translucent wall, drip-free spout, oil and petrol resistant material.
For brands: your cup in your colours
We manufacture custom injection moulded measuring cups: graduations matched to your range's ratio, tinting and branding. A useful object that stays in your customers' workshop for years. Send us your project: answer within 24 to 48 hours, the study is free.
