What Petrol for a Lawn Mower?

Written By:
Scott Carroll
Published On:
October 18, 2023
Adding fuel to mower

In our gardening journey, it’s not just the plants that matter but also the tools that help us achieve that perfect lawn. We often grapple with one pivotal decision: selecting the right mower fuel. Make the wrong choice, and you risk engine damage; choose wisely, and you ensure your mower’s optimal performance and longevity. Different fuels have unique pros and cons, and being informed is essential.

What petrol do you put in a lawn mower?

It’s more complex than just filling up at the nearest petrol station when discussing fuelling our mowers. The type of fuel we use plays a pivotal role in how our mowers perform. Most commonly, regular unleaded petrol is the go-to choice for many Australian gardeners. However, the decision becomes more complex with the rise of ethanol blends like E10. Using the wrong fuel can lead to issues like engine corrosion, especially if stored improperly. On the other hand, the right fuel ensures smooth operation and a longer engine life. It’s a choice that drives the health of our mowers.

Understanding different fuel types

Navigating the world of fuel types can feel like a maze for many of us. Each type comes with its unique set of characteristics, impacting how our mowers function and last. By delving deeper into the specifics, we can make informed choices, ensuring our trusty mowers get the best they deserve.

Regular unleaded petrol

Regular unleaded petrol is often the first choice for many Australian gardeners, and for good reason. It’s a tried and tested fuel that has powered our mowers for years. Comprising a straightforward blend without the added complexities of ethanol or higher octanes offers consistent and reliable performance. Most lawn mowers are designed to run efficiently on this fuel type, making it a safe bet for ensuring optimal engine health and longevity. The classic choice rarely lets us down in our gardening endeavours.

Ethanol blends (E10)

E10 is more than just a buzzword in the fuel world; it’s a blend gaining traction, especially at the pumps. Comprising 90% regular unleaded petrol and 10% ethanol, E10 is often seen as a more environmentally friendly option. However, while it might be kinder to the planet, it’s not always the best mate for our mowers. The ethanol component can absorb moisture from the atmosphere, leading to potential engine corrosion over time. While some modern mowers are designed to handle E10, knowing its effects and ensuring our equipment is compatible are crucial. It’s all about striking the right balance for the health of our mowers and the environment.

Higher octane fuels

Venturing into the realm of higher-octane fuels, we find options that are often associated with high-performance vehicles. But do our mowers need them? Higher octane fuels, such as 95 or 98, are designed to resist knocking in engines, ensuring smoother combustion. While this might benefit that sports car you’ve been eyeing, it can be overkill for our everyday mowers. In fact, using these fuels without necessity can lead to increased costs without any tangible benefits in performance. However, the manufacturer might recommend a higher octane in certain situations, especially with high-end or specialised mowers. Knowing our equipment and choosing wisely is essential, ensuring we’re not just burning money without reason.

What fuel should I use in my lawn mower?

The quest for the ideal fuel for our mowers can seem daunting, but when we break it down, it’s all about understanding our equipment and priorities. For the majority of standard mowers, regular unleaded petrol is the champion. It’s reliable, widely available, and suits most engine types. If you’re leaning towards E10 for its environmental benefits, ensure your mower is compatible to avoid unwanted engine woes. And while higher octane fuels might sound fancy, they’re best reserved for specific mowers requiring them. Always consult your manufacturer’s recommendations, and consider your mower’s environmental and long-term health. After all, the right fuel choice is the key to many more seasons of lush, green lawns.

Yard Work recommendation: Best petrol for 4-stroke mower

Regarding 4-stroke mowers, a staple in many Australian backyards, our recommendation at Yard Work is clear: stick with standard 91-octane unleaded petrol. Over the years, we’ve seen that this fuel offers a consistent and reliable performance for these mowers. It provides the right balance of efficiency without the potential complications arising from ethanol blends or higher octane fuels. Moreover, it’s readily available at most service stations, making it a convenient choice. Based on our experiences and insights from experts like those at Small Engine Warehouse Australia, it’s the safest bet for ensuring your 4-stroke mower runs smoothly season after season.

man on ride on mower

If you want to learn more about 4-stroke mowers, check out our best petrol lawn mower roundup here!

Diving into the ethanol debate

Ah, the ethanol debate – it’s a topic that’s been stirring the pot in the gardening community for a while now. As we strive for more environmentally-friendly choices in all our lives, the question arises: is ethanol-blended fuel the way forward for our mowers? While it promises reduced emissions and a smaller carbon footprint, it also raises concerns, especially for our trusty lawn companions. As we delve deeper into this debate, we’ll weigh the pros and cons, aiming to shed light on whether ethanol truly has a place in our mower’s fuel tank or is just a passing trend.

Benefits of ethanol in fuel

Ethanol-blended fuels have made a mark, and it’s not without reason. Here are some of the advantages we’ve observed:

  • Environmentally friendly: One of the standout benefits of ethanol is its green credentials. It’s a renewable resource derived from organic materials like corn, reducing our dependence on fossil fuels.
  • Reduced emissions: Ethanol burns cleaner than pure petrol, leading to reduced greenhouse gas emissions. This is a significant plus for those keen on reducing our carbon footprint.
  • Economic benefits: Supporting ethanol production can boost local agriculture, providing economic benefits to farming communities.
  • Performance boost: Some users have noted a slight performance boost when using ethanol blends, especially in newer mower models designed for it.

Drawbacks of ethanol in fuel

However, it’s not all sunshine and rainbows with ethanol. Here are some concerns that have cropped up:

  • Moisture absorption: Ethanol has a knack for attracting moisture from the atmosphere. In a mower’s fuel system, this can lead to corrosion and other issues over time.
  • Shorter shelf life: Ethanol-blended fuels, like E10, degrade faster than pure petrol. If you’re storing fuel for extended periods, this can be problematic.
  • Engine compatibility: Not all mowers are designed to handle ethanol blends. Using E10 in an incompatible engine can reduce performance and potential damage.
  • Fuel efficiency: Some users have reported reduced fuel efficiency with ethanol blends, meaning more frequent refuelling.

As with most things, it’s about finding the right balance. While ethanol offers some clear benefits, it’s essential to be aware of its drawbacks, especially regarding our mowers.

Fuel additives and stabilisers

Venturing into fuel additives and stabilisers, we find ourselves amidst a world of solutions designed to enhance our mower’s performance and longevity. Over the years, we’ve come to appreciate their role, especially when dealing with the quirks of ethanol-blended fuels. Let’s dive into what they bring to the table:

  • Combatting ethanol’s moisture problem: One of the primary roles of fuel stabilisers is to counteract ethanol’s tendency to absorb moisture. By doing so, they prevent water from settling at the bottom of the fuel tank. This common issue can lead to engine corrosion and starting problems.
  • Extending fuel shelf life: We’ve all been there – storing fuel for the off-season, only to find it degraded when needed. Additives can extend the life of both regular and ethanol-blended fuels, ensuring they remain fresh for longer.
  • Enhancing performance: Some additives are designed to clean the fuel system, removing deposits that can hinder performance. The result? A smoother-running mower that’s more efficient.
  • Protecting the engine: Beyond just the fuel system, certain additives protect the engine, reducing wear and tear and ensuring a longer lifespan.
  • Economic benefits: While there’s an initial cost to purchasing these additives, the long-term savings in reduced maintenance and repair costs can be significant.

In our gardening journey, we’ve found that while ethanol-blended fuels come with challenges, the right additives and stabilisers can make a world of difference. They bridge the gap, allowing us to enjoy the benefits of ethanol without the associated headaches. It’s like having a trusty sidekick, ensuring our mowers are always at their best.

Fuelling lawn mower: Best practices

Fuelling our mowers might seem straightforward, but over the years, we’ve realised that a little care ensures our equipment’s longevity. Here’s our step-by-step guide, honed from years of experience, on fuelling your mower the right way:

  1. Check the manual: Always refer to your mower’s manufacturer manual before anything else. It’ll provide specific recommendations on the fuel best suited for your machine.
  2. Safety First: Ensure the mower is on a flat, stable surface. If you’ve just used the mower, wait for the engine to cool down. Also remember that hot engines and fuel don’t mix well. We recommend keeping a fire extinguisher nearby, just in case.
  3. Use a Clean Funnel and Container: Always use a clean funnel and container when refuelling. Any debris or contaminants can cause engine problems down the line.
  4. Don’t Overfill: Fill the tank to about 95% capacity. This allows for fuel expansion, especially on hot days, preventing spillage or leakage.
  5. Tightly Seal the Fuel Cap: Once done, ensure the fuel cap is tightly sealed to prevent any evaporation or contamination.
  6. Regularly Check for Leaks: After refuelling, check for any signs of leaks. If you spot any, address them immediately.
  7. Dispose of Old Fuel Safely: If you have old or stale fuel, don’t just pour it into your mower. Dispose of it safely, following local regulations.
  8. Clean Up Any Spills: If you spill any fuel, clean it up immediately. It’s not just a fire hazard but can also harm your lawn.
  9. Regular Maintenance: Regularly check and clean your mower’s fuel system. It ensures optimal performance and reduces the chances of any fuel-related issues.

Fuelling our mowers might seem like a small task in the grand scheme of gardening, but these little things often make the most significant difference. By following these best practices, we ensure our mowers are always ready to give us that perfect lawn, season after season.

A note on checking oil levels

Oil and fuel go hand in hand to ensure our mower’s optimal performance. Think of them as the dynamic duo that powers your machine. Here’s why they’re crucial:

  • Lubrication: Oil lubricates the engine’s moving parts, reducing wear and tear. Without adequate oil, the engine can overheat and wear out faster.
  • Cooling: Along with lubrication, oil helps cool down the engine by dispersing heat.
  • Checking oil levels: Before every use, checking the oil level is a good habit. Ensure the mower is on a level surface, remove the dipstick, wipe it clean, reinsert it, and then check the level. If it’s low, top it up with the recommended type of oil.
  • Changing oil: Oil can get dirty over time and lose effectiveness. As per the manufacturer’s recommendations, regularly changing the oil ensures your engine remains in tip-top shape.

In our gardening journey, we’ve found that a little attention to oil levels and quality can make a world of difference. It’s the secret sauce that, along with the right fuel, ensures our mowers are always at their peak performance.

Checking oil levels

Storage for longevity of fuel

Ah, the age-old question of how long our fuel stays good for and how best to store it. Over the years, we’ve seen many gardeners caught out by stale fuel, leading to a mower being more reluctant to start than a teenager on a Monday morning. Here’s what we’ve learned about the longevity of different fuels and how to store them:

  • Regular unleaded petrol: This trusty fuel remains fresh for about a month. After that, it degrades, losing its combustibility and potentially harming your mower’s engine.
  • Ethanol blends (E10): The shelf life of E10 is even shorter, often lasting only a few weeks. The ethanol component can absorb moisture from the air, leading to separation and potential engine issues.
  • Higher octane fuels: These tend to last longer than regular unleaded, but using them within a month or two is still a good practice.

Storage tips

  1. Fuel stabilisers: If you know you won’t use your fuel for a while, consider adding a fuel stabiliser. It can extend the life of your fuel, making it last several months without degrading.
  2. Store in a cool, dry place: Heat and moisture are enemies of stored fuel. Keep your fuel containers in a cool, dry place, away from direct sunlight.
  3. Use a dedicated fuel container: Always store fuel in a container designed for it. These containers are sealed to prevent moisture ingress and evaporation.
  4. Off-season equipment storage: If you’re storing your mower for an extended period, like over winter, it’s a good idea to drain the fuel or add a stabiliser. Also, consider running the mower until it’s out of fuel. This ensures there’s no stale fuel left in the system, which can gum up come springtime.
  5. Regularly check stored fuel: Before using stored fuel, check it. If it smells off or looks cloudy, it’s best to dispose of it safely and get fresh fuel.

A little foresight when it comes to fuel storage can save a lot of headaches down the line. By ensuring our fuel remains fresh and our equipment is stored correctly, we’re all set for a hassle-free start to the next gardening season.

Final thoughts

Choosing the right fuel and caring for it might seem like a small cog in the vast machinery of gardening, but its impact is profound. The right choice ensures our mowers run smoothly, our gardens flourish, and our efforts bear fruit. As we’ve journeyed through the nuances of fuels, additives, and best practices, one thing stands clear: a little knowledge and care go a long way. So, as we gear up for another season of lush lawns and blooming flowers, let’s fuel our passion with the same diligence we fuel our mowers. Here’s to many more seasons of green perfection!


How often should I clean my lawn mower’s fuel system?

Regular maintenance is key to a mower’s longevity. It’s recommended to clean the fuel system at least once a season or after every 50 hours of use, whichever comes first.

Can I mix different types of fuel in my lawn mower?

It’s best to avoid mixing different fuels. Stick to the manufacturer’s recommendation and always use fresh fuel for optimal performance.

What are the signs of bad or stale fuel in my lawn mower?

Signs include difficulty starting the mower, uneven running, stalling, or a foul odour from the exhaust. If you suspect stale fuel, it’s best to drain and replace it.

How can I dispose of old or stale fuel from my lawn mower?

Never pour old fuel down drains or into the ground. Check with local waste disposal sites or recycling centres, as many offer safe disposal options for old fuel.

Are electric lawn mowers a viable alternative to petrol-powered ones?

Both corded and battery-operated electric mowers are gaining popularity due to their eco-friendliness and reduced maintenance. They’re especially suitable for smaller lawns and gardens.