The Right Mix Ratio for Your Grass Trimmer

Using the correct fuel mixture is vital to your grass trimmer’s performance and longevity. Incorrect fuels or mix ratios can lead to piston seizure, excessive wear, and reduced lifespan. The correct STIHL mix ratio is:

STIHL 2-stroke engine oil: 1:50 = 1 part oil + 50 parts petrol

If you use a different brand of two-stroke oil, ensure it meets the correct TC classification under one of the following standards: JASO FB, JASO FC, JASO FD, ISO-L-EGB, ISO-L-EGC or ISO-L-EGD. Use the same 1:50 ratio (1 part oil to 50 parts petrol).

To achieve a 1:50 ratio fuel mix:

• 5 litres of petrol + 0.1 litres (100 ml) of oil = correct mix
• 1 litre of petrol + 20 ml of oil = correct mix

Always measure accurately — too much oil can cause smoke and fouling, while too little oil can damage your engine.

Use unleaded petrol with a minimum octane rating of 90 RON. In the UK, regular unleaded petrol (95/97/98 RON) is ideal and more environmentally friendly.

For best results, use fresh, high-quality petrol and avoid old or contaminated fuel.

Always use high-quality 2-stroke engine oil that meets TC standards. STIHL 2-stroke engine oils are specially formulated for STIHL tools and help extend the service life of your grass trimmer.

Caution: Inferior oils can damage the engine, seals, and fuel tank.

When mixing fuel, use a fuel-safe container such as a STIHL combination canister. Add the oil first, then the petrol, seal the container, and shake to mix. Open carefully, as pressure may build up inside.

Gustharts is a STIHL Approved Dealers offering expert guidance and servicing support for all STIHL products. Get advice on fuel mixing, maintenance, and tool care directly from your local specialist.

You can download the official STIHL grass trimmer operating instructions for your model from our website for free. Always consult these for maintenance, refuelling, and safety guidance.

To avoid any risk of incorrect mixing, choose STIHL MotoMix — our premium pre-mixed fuel containing no ethanol. It’s ready to use, formulated for optimal performance, and offers a long shelf life with reduced emissions.

Contact your local STIHL dealer for more information on MotoMix and its compatibility with your trimmer.

• Use the correct 1:50 mix ratio (1 part oil to 50 parts petrol).
• Always use high-quality 2-stroke oil with TC classification.
• Mix fuel in a fuel-approved container and shake thoroughly.
• STIHL MotoMix provides an easy, ready-mixed alternative with no ethanol.
• Using the right mix protects your engine from damage and extends its service life.