How to mix 2-stroke petrol

How to mix 2-stroke fuel for your 2-stroke petrol engines

Mixing 2-stroke

Mixing 2-stroke fuel for your small engine is relatively straightforward so long as you have a means of accurately measuring your petrol and oil in the quantities you require.

For example, if you need to mix 5 litres of 2-stroke fuel at a 50:1 ratio, you will need 5 litres of petrol and 100ml of oil. To correctly mix to this ratio you will need a means of measuring both 5 litres of petrol and 100ml of 2-stroke oil.

This could be:

• a 5 litre can and a separate 100ml measuring jug
• a 5 litre can and an individual 100ml bottle of oil
• a dedicated, semi-transparent mixing bottle with a fill line at 5 litres and another line 100ml above

You should usually mix your petrol and oil before adding it to your engine's fuel tank. Add the petrol and oil into your mixing container and give a gentle shake to mix the two together.

After mixing the 2-stroke, simply fill the fuel tank on your engine and you are good to go.

Occasionally, some engines do have separate tanks for fuel and oil and will meter them automatically - but this is rare with garden machinery.

Due to the risk of stale fuel you shouldn't store 2-stroke mix for more than 30 days. If you have no plans to use your machine within the next 30 days, we'd recommend either draining your fuel tank or running it dry before storing your machine away.

What is the ratio for 2-stroke fuel mix?

Most modern petrol garden machinery requires a 50:1 ratio mix of petrol to oil. This means for every 1 litre of petrol you must mix 20ml of oil. We've listed some of the common quantities and the petrol to oil mix below.

The required petrol to oil ratio can differ between engines and brands of oil. The best thing to do is refer to your user manual and follow manufacturer guidelines.

Please be aware that some older 2-stroke engines (and some lower quality modern engines) may require a different petrol to oil ratio, such as 20:1, 25:1 or 40:1. It's important to ensure you use the correct ratio for your engine and the grade of oil used.

Here's a handy PDF which you can download and print which shows some of the common ratios and mix quantities for petrol and oil. Download and print it here.

Why do I need to mix oil with my petrol?

Unlike a 4-stroke engine, 2-stroke engines generally don't have a separate oil reservoir for lubrication. So, in order to keep your 2-stroke engine lubricated the fuel must contain a certain amount of oil.

The petrol to oil ratio for your engine will be published by the manufacturer. Please check your user manual.

What happens if I mix the wrong ratio, or don't mix oil at all?

It's important that you be as accurate as possible when mixing your fuel-oil ratio.

If there is too little oil

Too little oil in your 2-stroke fuel will lead to serious damage in the engine because of a shortage of lubrication.

If there is too much oil

Too much oil will mean that you are burning more oil than needed, making your engine "smokey" and you'll see oily residues around the exhaust.

Prolonged use of mix with too much oil can result in carbon deposits in the engine, which will lead to performance issues and potential long term damage.

Either way, you could face costly repairs so it's strongly recommended you are able to mix your 2-stroke fuel accurately.

What grade of 2-stroke oil do I need?

There are many different grades of 2-stroke oil and it's important that you use the correct oil for your engine. Your owners manual will specify the correct grade of oil. Most manufacturers have oils developed specifically for use with their engines, so where possible we'd always recommend using the brand of oil to match the brand of engine.

Discover our range of mineral and synthetic 2-stroke oils from STIHL and Morris Lubricants.