Wondering what type of petrol is used in a petrol lawn mower’s fuel system? Are there any fuel types that are better than others? And which petrol types should you avoid?
Find all the answers to these questions and more in this guide.
✅Key Takeaways:
The best type of petrol to use in a petrol lawn mower is standard unleaded petrol, ideally with an ethanol content of 5% and a minimum 87 octane rating.
We don’t recommend using E10 fuel in most petrol mowers because the higher ethanol content in the fuel could damage and corrode a mower’s small engine.
Premium petrol doesn’t have the same benefits in a small petrol mower as it does in a car engine, so there’s no need to waste your money on a premium fuel product.
Table of Contents
🤔 What Type Of Petrol Should You Use In A Petrol Lawn Mower?
In the UK, the type of petrol you should use in the vast majority of lawn mowers is standard unleaded petrol. “Super unleaded” petrol is a popular choice for petrol mowers because it has a low ethanol content of just 5%.
Newer mower engines can also use E10 petrol, which was introduced in 2020. However, older mowers can’t run on E10 due to the risk of corrosion damage to their engines. We’ve discussed this in more detail later.
You should never use petrol with an ethanol content that exceeds 10% in your lawn mower, regardless of how new the engine is – again due to the potential for corrosion damage.
💰 Where Can You Buy Fuel For A Petrol Lawn Mower?
There are a few different places you can buy fuel for a petrol lawn mower in the UK:
From a petrol station. The easiest way to get hold of unleaded or super unleaded petrol for your lawn mower is simply by filling a petrol can with fresh fuel at your local petrol station. If you’re wondering, we use this S Style CAN2 Unleaded Petrol Can (< Amazon link).
From a garden centre. Most decently sized garden centres also sell various types of fuel for garden machinery and power tools. Convenient, but (in our experience) expensive.
Online. A few brands have started selling fuel online recently. You can find everything on Amazon nowadays, and that includes petrol. The Aspen 4-Stroke Petrol has good reviews, and could be a convenient option if you’d rather order petrol straight to your home.
🧐 What’s The Difference Between 2-Stroke And 4-Stroke Mower Fuel?
2-stroke and 4-stroke lawn mowers don’t use different fuel – both use unleaded petrol. This applies to all petrol mower types, including push mowers and self-propelled mowers.
However, the way that you use this fuel differs in 2-stroke and 4-stroke mowers.
With a 2-stroke lawn mower, you need to separately mix the fuel and oil before you add it to the fuel tank. Rather than the motor drawing oil from a different compartment, it draws the petrol-oil mix direct from the fuel tank and uses it to lubricate the engine internals.
A 4-stroke lawn mower is easier to fill with fuel – you simply pour the fuel straight into the tank and top up the oil in a separate compartment.
🤷♂️ Can You Use E10 Petrol In A Lawn Mower?
E10 fuel contains 10% ethanol and 90% unleaded petrol (hence the name E10 – as in, ethanol 10%).
In 2021, E10 petrol was introduced by the UK government as a greener fuel, with the aim of reducing greenhouse gas emissions, promoting cleaner air, and addressing environmental concerns associated with the use of standard unleaded petrol.
Most new mower engines can be used with E10. However, old engines aren’t designed for use with E10 fuel, so you shouldn’t use this fuel if your petrol lawn mower is more than two years old.
The problem with E10 fuel is that in smaller engines like mower engines, it may cause corrosion and engine damage. Ethanol attracts water, leading to increased moisture content in the fuel system. This can corrode metal parts and lead to clogged fuel filters, carburettor issues, and potential engine malfunction.
So, despite the undoubtedly noble efforts of the UK government to reduce greenhouse emissions with the E10 launch, it’s not ideal for all situations.
In our opinion, E10 petrol should only ever be used as a last resort in a lawn mower engine, regardless of the mower’s age.
😖 What Happens If You Use The Wrong Type Of Fuel In A Petrol Mower?
If you use the wrong type of fuel in a petrol mower, your mower might overheat, stop running, or die completely due to engine failure.
Always check your user manual to confirm the recommended fuel type for your mower, especially when using a new mower, or if you can’t remember the type of fuel you usually use.
If you’ve added the wrong fuel by mistake, it’s not the end! Just drain the fuel from the tank as thoroughly as possible and start again with the correct fuel.
🤯 Can You Use Diesel In A Petrol Mower?
No. Just as you should never use diesel in a petrol car, you should never use diesel in a petrol mower.
Petrol engines and diesel engines operate on different combustion principles. The design and components of the engines, including the fuel injection system and ignition systems, are tailored to the specific characteristics of the fuel they are intended to use.
In case you’re curious as to what would theoretically happen if you put diesel in a petrol lawn mower, you’d likely damage the engine, causing misfiring. Your mower engine might blow out smoke, cut out, or fail to start at all.
We tried to find a video of somebody demonstrating what might happen if you put diesel in a petrol mower, but unfortunately, it seems nobody wanted to ruin their lawn mower for the cause.
However, we did find this vintage Fifth Gear video of putting petrol in a diesel car, which surprisingly didn’t end as disastrously as expected:
Don’t try this at home!
🏍 Will A Lawn Mower Perform Better With Premium Petrol?
No, using premium petrol won’t improve the performance of your lawn mower. A mower’s engine is too small for the investment to be worthwhile.
Premium petrol is, as the name suggests, more expensive than standard petrol. It typically has a higher octane rating (usually 91 or higher in the UK), which means it’s less likely to cause engine knocking. This, in turn, helps the engine to run more smoothly.
Lawn mowers, with their small petrol engines, aren’t designed to take advantage of the higher octane rating found in premium petrol, so you may as well save your money and buy a cheaper fuel.
🏁 Final Word
Thanks for taking the time to read this article! You should hopefully have found the answer you were looking for.
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