2 Stroke Engine Oil - How to Work out the Correct Mix Ratio

We have put together an easy guide to calculate the correct petrol to oil ratio for a 2 stroke engine.

Firstly, make sure you check your owners manual for the recommended oil and petrol ratio mix that is required for your machine.

The Maths behind the Ratio

The following equation will allow you to easily calculate the correct amount of oil needed to mix with the petrol you already have.

The example we will use is a 50:1 ratio, this is a common ratio used for a variety of 2 stroke engines.

Step 1:

Firstly, we will show you how to identify the millilitres

You will need to divide 1 Litre (1000ml) by the 50 in the ratio (see example below).

1000 / 50 = 20

This gives us a result of 20.

Step 2:

Next, we will show you how to calculate the amount of oil needed - dependant on the amount of petrol you already have and the millilitres we have just identified in step 1.

Now we need to times the amount of petrol/ gasoline by the amount of millilitres (which is 20ml from step 1), in the example below we will say we have 2 Litres of petrol.

2 x 20 = 40

The result we have is 40 which tells us we need 40ml of oil.

This equation works for any amount of petrol. For example, if I have 5 Litres of petrol I would times 5 x 20 and this would give me a result of 100ml.

Recap:

Here is a recap of the equation:

1000 / ratio = ml

Litres of petrol x ml = oil needed

Smart App Alternatives

Above is the manual method for working out the correct engine oil to petrol ratio.

However, there are apps that can be downloaded to your smart device that will do the equation for you. One particular app that we found useful is the Castrol 2TRatio app.

It is available to download from:

• The Apple app store
• The android Google play app store