What’s The Best Petrol For My Lawn Mower?

Wondering what’s the best type of fuel to use in your petrol lawn mower?

In this guide, we’ll explain what type of petrol to use in your mower.

We’ll also explain how to buy lawn mower fuel, and how to store it safely.

What’s the best petrol for a lawn mower?

Man refueling lawn mower.

The best petrol for your lawnmower is unleaded petrol, with an octane rating of at least 87 (91 RON). Importantly, the petrol cannot have an ethanol content of more than 10% (E10 petrol). If there’s too much ethanol in the fuel, it can attract water, which sinks to the bottom of the fuel, allowing bacteria to breed and causing corrosion to your lawn mower. E15 petrol, which is becoming more common in the UK, should not be used in your lawn mower.

Most people use 95 RON unleaded petrol in their lawn mower. There is little benefit in using premium fuels in small engines such as your lawn mower.

The dangers of stale petrol

To keep your mower running smoothly, the lawn mower fuel you use must be fresh. Old petrol can become stale in as little as a few weeks if left in contact with the air. Using stale petrol in your lawn mower can result in poor performance, will make the engine run rough, and may make the lawn mower difficult to start with the starter cord.

Petrol can also become stale inside the lawn mower engine. After your finish mowing your lawn, it’s a good idea to clear any petrol out of the engine and fuel system – if the fuel is stored in the fuel tank, it won’t become stale as easily as it does inside the engine itself.

To clear fuel out of the engine when you finish mowing, switch the fuel valve to the off position and start up the motor. Leave it running for a few minutes until it cuts out – when it stops, this means that all the fuel has been purged from the carburettor and fuel system.

How to store lawn mower fuel and prevent it from going stale

Green British jerry can.
This is the 5 litre jerry can used to store petrol in the UK.

To prevent your lawn mower fuel from becoming stale, you should store the petrol in an airtight jerry can, out of direct sunlight.

If you need to store gasoline for an extended period of time, you can use a fuel stabiliser, which is a type of fuel treatment product. Essentially, you treat the fuel with a stabiliser prior to storing it. The fuel stabiliser then helps to prevent gum or varnish buildup, and prevents these deposits from entering the fuel system and carburettor. This helps to prevent engine damages and makes the mower much easier to start.

Most petrol will begin to go stale after 30 days, but with a petrol stabiliser used, the fuel should last in storage for two years or even longer.

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For safety, you should keep the petrol in a well-ventilated area far away from your dwelling. Petrol should also be kept away from any potential ignition triggers such as sparks and electronic equipment. A garage or shed is a good place to store petrol for most people.

There are also rules about the amount of gasoline you can keep at home – the current rule in the UK is a maximum of 30 litres, which is a lot more than you need to keep a lawn mower running. You probably only need to buy two or three litres of fuel for your mower, unless you have a very large garden.

How to make your mower run smoother

Other than ensuring that you use fresh unleaded petrol with the right octane rating and not too much ethanol, there are some other steps you can take to make the motor run smoother, and make it easier to start.

  • Clean the fuel filter – it might be clogged up with gunk if the mower is more than two years old. You can wipe any dirt or debris off and then spray the filter with a cleaning product, or you can replace the fuel filter completely.
  • Change the spark plug – it might be dirty or worn out.
  • Run fresh fuel through the system with an additive applied. If you’ve previously used old petrol or low quality fuel, flushing it out can help the motor to run more smoothly.

These tips can also be helpful for increasing the longevity of your mower. Although petrol lawn mowers are very tough, it’s important to maintain them properly to extend their lifespan.

2-stroke vs 4-stroke mower fuel

Man refueling a 4 stroke mower.

2-stroke and 4-stroke lawn mowers can use the same type of fuel – unleaded petrol with at least an 87 octane rating and no more than 10% ethanol. This applies to both self-propelled and push lawn mowers.

The difference between the two types of petrol mowers is how you use this fuel.

With a 4-stroke lawn mower, you simply pour fuel into the fuel tank, just like with your car.

However, with a 2-stroke lawn mower, you need to mix fuel and oil together, separate to the fuel tank, before pouring the mixture into the mower. This is because the gasoline in a 2-stroke mower helps to lubricate the engine internals, rather than the motor drawing oil from a separate reservoir.

How do I get petrol for a lawn mower?

You can buy fuel for your petrol lawn mower at most petrol stations. They should sell the correct type of jerry can, which should be a green plastic container, for you to store the petrol in safely.

When transporting fuel, there are no laws about how much gasoline you can store in your car. However, the police can stop you if they think the amount of petrol or the way in which you’re transporting it is hazardous.

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