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The right fuel mixture for your petrol grass trimmer or brush cutter

Your gas grass trimmer runs on a fuel mixture made up of gas and engine oil. Use the right weed eater mix ratio to keep tools at their best for years to come.

12.11.2024

A man filling the fuel tank of a STIHL grass trimmer from a large bottle with shrubs behind him

How to mix gas for weed eater

It’s important to power your grass trimmer or brush cutter with a fuel mixture made to the right recipe: unsuitable fuels and the wrong mix ratios can cause serious damage, leading to piston seizure, excessive wear, and ultimately a shorter lifespan for your grass trimmer. The mix ratio you need to remember when making up fuel mixture for your trimmer is: 

How to mix 2 stroke fuel for weed eater

1:50 = 1 part oil + 50 parts gas 

When using other products

Any two-stroke oil you use in your grass trimmer must have the TC classification, and you can use the same ratio for your fuel mixture as with the STIHL engine oil:

1:50 = 1 part oil + 50 parts gas

A man pours STIHL HP 2-stroke engine oil into a measuring beaker

Working out proportions 

Example fuel mixture proportions 

You can achieve a fuel mix ratio of 1:50 with 5 l of petrol and 0.1 l (100 ml) of oil. 

What type of gas should I use in my fuel mixture?

The petrol in your grass trimmer fuel mixture needs a minimum octane rating of 90 RON; the gas that is widely available at UK petrol stations is unleaded and rated at  RON, which is better for users’ health and the environment too. Use high-quality fuel for best performance. 
A collection of canisters including a bottle of STIHL HP Super 2-stroke engine oil and an orange combination canister

What type of engine oil should I use in my fuel mixture?

You should only use high-quality oil for 2-stroke engines, that meets the requirements for TC classification. We recommend STIHL 2-stroke engine oil, which is specially formulated for STIHL tools and will prolong the life of your grass trimmer. 

Caution: Inferior products can damage the engine, sealing rings and fuel tank of your trimmer. 

Information on mixing: Make up your grass trimmer fuel mixture in a vessel that is approved for use with fuels – STIHL sells combination canisters that are ideal. Pour in the oil first, followed by the petrol; seal the canister and give it a good shake to combine the fuel mixture. Now you’re ready to use the fuel mixture in your grass trimmer or brush cutter tank. Take care as you open the canister, in case pressure has built up inside. 

STIHL grass trimmer fuel mixture

Trimmed grass in the foreground, with long, unruly brush behind it.

The right fuel mixture for your grass trimmer – no mixing required

Using unsuitable fuel or an inappropriate mix ratio could damage your grass trimmer. The easy way to give your STIHL tools the best treatment is by opting for STIHL MotoMix fuel, a premixed fuel mixture that contains no ethanol, is specially formulated for our tools and guarantees high performance and a long service life.

Summary: How to mix gas for weed eater

  • Using the right fuel mixture in your grass trimmer protects it from damage such as piston seizure 
  • We recommend using STIHL 1:50 2-stroke engine oil with gas , at a mix ratio of 1:50 – 1 part oil to 50 parts of petrol 
  • If you’re using a different brand of oil, make sure it has the TC classification. The same mix ratio of 1:50 applies 
  • STIHL MotoMix is perfect for your petrol grass trimmer – it’s an ideal fuel mixture that is already blended and specially formulated for the engine. It creates low emissions with high performance and boasts a long shelf life 

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