What is premixed fuel?

Premixed fuel is made by adding two stroke oil into standard unleaded petrol. As two stroke engines do not have an internal oil reservoir (or sump), the oil is mixed in with the fuel. This allows the mixture to lubricate the engine, while also acting as a source of ignition for internal combustion. 

Note: Some two stroke engines may have an external oil tank and a pump which automatically feeds the oil into the combustion chamber. These engines DO NOT require premixed fuel in order to run. If you are unsure about your premix fuel requirements, it’s best to consult your user manual, or ask your local outboard dealer.

Why is the fuel / oil ratio important?

Every two stroke engine will operate with an optimal ratio of fuel to oil. If there is too much oil in the mix, the spark plug may not be able to ignite the fuel in the chamber, and the engine will not run. If there is not enough oil in the mix, the piston will not receive enough lubrication. This can lead to premature wear of the piston, rings, and engine bearings, and in some cases – cause a catastrophic failure in the engine. That’s why it’s important to maintain the appropriate amount oil in your premix fuel, to prevent this from occurring. Best practice is to keep your premix stored in a separate fuel container, that is labelled with the correct ratio of fuel to oil, and the date the fuel was mixed.

Why is the mixed date important?

After 30 days of exposure to air and other environmental factors, unleaded fuels will suffer from a reduction in quality, or turn “stale”. This does two things; First of all, it will raise the ignition point of the fuel. Secondly, the fuel will begin to varnish or “gum up”. Best case scenario, this fuel will cause your engine will run less efficiently. Worst case, the jets in your carburetor may become clogged. This will prevent an adequate amount fuel from entering the engine. If you have other two stroke appliances that use the same ratio of premix, such as lawn mower or edge trimmer, it’s best to cycle your fresh premixed fuel through this equipment and replenish your supply as required. This will ensure the optimal performance of your engines.

Using the calculator

1. Input the amount of fuel that you want to mix, in litres (L).
2. Select the fuel / oil ratio that corresponds with your engine.
3. The amount of oil required will automatically calculate below.
   Note: The amount of oil is calculated in millilitres (ml)