Short answer
Many two-stroke petrol hedge trimmers use a 50:1 petrol-to-oil mix (2% oil), but some specify other ratios. Check your manual and the fuel cap or tank label. Four-stroke petrol hedge trimmers use plain fuel in the tank and oil in the engine, not mixed fuel.
Two-stroke vs four-stroke
| Type | Fuel | Notes |
|---|---|---|
| Two-stroke | Petrol mixed with two-stroke oil | Most petrol hedge trimmers; ratio set by the manufacturer |
| Four-stroke | Plain petrol; separate engine oil | Check the manual for the oil type and level |
How to mix
- Use fresh unleaded petrol and the oil type the manufacturer specifies.
- Measure the oil carefully into an approved fuel container.
- Add the petrol, close the container and shake to mix.
- Label the container and the date; do not store mixed fuel for long periods.
- Fuel outdoors, away from ignition sources, with the engine off and cool.
Example ratios
| Ratio | Oil per 1 litre of petrol |
|---|---|
| 50:1 | 20 ml |
| 40:1 | 25 ml |
These figures are the arithmetic for those ratios only. Your model’s required ratio comes from the manual.
If you used the wrong mix
Too little oil can damage the engine; too much oil causes smoke and fouling. Drain the tank and refill with the correct mixture, and ask a dealer if the engine ran with the wrong mix.
Always follow your own manufacturer’s manual: procedures, fuel mixes and service intervals differ between models, and a manual overrides any general guide.