Petrol Lawn Mower Maintenance 101

Petrol lawn mower

Petrol lawn mowers are super handy contraptions, but they require a bit of special love, care, and attention to keep them running. If you’re new to the homeowner scene (or have just been lucky enough to never mow a lawn), it’s likely you have questions. Luckily for you, DreamyHome is your source for all things DIY and homeownership, and lawn mowers (petrol or otherwise) are absolutely in our wheelhouse.

So what’s on the docket today?

Today’s Topics Include:

That was a mouthful! Now, without further ado, let’s get you some well-deserved answers.

Petrol Lawn Mower Q & A:

Now, the web is full of questions related to all sorts of things, and petrol lawn mowers are no exception. As such, we felt it was time to scrape up a few answers for the most commonly asked questions about petrol lawn mowers.

Do Petrol Lawn Mowers Need Servicing?

Petrol riding lawn mower

Okay, first things first – this is one of those questions that shows a basic misunderstanding of general household tools, so let’s establish something really quickly.

Any tool that you regularly use will need servicing in some way, shape, or form as the years go on. This is absolutely vital to ensuring your tools stand the test of time, no matter how little you use them.

So in short, yes! Service and clean your tools, petrol lawn mowers included. The longer answer, however, will take a bit longer to answer.

While we’ll get into the specifics of what to service and when later in this article, there are a few general guidelines to follow:

  • Clean:
    • Thoroughly clean your lawnmower with a damp cloth (no soap). Be sure to get all moisture off any parts that you clean to prevent corrosion.
    • Remove any debris in every nook and cranny.
    • Clean your carburettor.
    • Cleanse your spark plug.
    • Clean and/or replace the air filters as needed.
  • Replace:
    • Replace/change your oil.
    • Inspect commonly-used and cleaned parts (carburettor, spark plug, blades, etc.) and replace those displaying ageing or failure.
    • Drain the petrol in your fuel tank when you’ll be cutting down on lawn mowing (usually over the winter).
  • Grease:
    • Grease any moving parts, especially joints, regularly with WD-40 (or an alternative of your choice).
  • Sharpen:
    • Sharpen and/or replace the blades on your lawn mower.

In short, treat your lawn mower like your car – take care of it and regularly inspect it.

Remember that your petrol lawn mower is literally an engine powered by tiny explosions, powering blades spinning at 2,500-3,000 RPMs. If you neglect a part, it can end up less than ideal to say the least.

How Often to Service a Petrol Lawn Mower?

Checking mower blades

The general rule of thumb is to service your petrol lawn mower at least once per year, and more often if you regularly use it or have a large property.

The best rule of thumb is to give it a bit of love and care once before beginning mowing season and once after mowing season has concluded. This will generally come out to cleaning it in spring, and once in late summer.

How Do You Service a Petrol Lawn Mower?

This is a hard question to answer in one section, but we’re going to try come hell or high water. The basics of servicing a petrol lawn mower are as follows:

  1. Follow all steps in the first subsection, namely:
    1. Clean everything thoroughly, sanding corroded bits – this includes the wheels, axis, and the lifting mechanism of your mower
    2. Replace parts as needed (if they show wear)
    3. Grease the mower’s joints and top off your oil, draining fuel when it will be out of use – this includes the wheels and axis
    4. Sharpen your mower blades
  2. Additional bits to remember:
    1. Check and clean/replace your air filters (detailed in the similarly-named sections below)
    2. Check and clean your carburettor (detailed in the section below)
    3. Inspect oil levels (detailed in the similarly-named section below)
    4. Double-check your cutting height, make adjustments as needed, and clean & lubricate the mechanism

And that’s that!

How Do I Clean the Carburettor on My Lawn Mower?

Petrol lawn mower repair

As we’ve already discussed, cleaning your lawn mower is vital to its long-term health. One of the most important bits you’ll need to clean is your carburettor – but how exactly do you do that?

I’m so glad you asked! Keep in mind that this will vary slightly by model and manufacturer, but this is a wonderful basic guide to get you started. Clean the carburettor on your lawn mower with the following process:

  1. Never clean a hot (recently-used) lawn mower. Wait for it to cool or you will burn yourself.
    1. Note: If you’re like me, you will likely find it helpful to photograph each part of the process so step 12 is easier (i.e. reassembly of the carburettor).
  2. Remove the engine cover if your lawn mower has one.
  3. Drain the petrol in your fuel line (especially if it has sat for a long time).
    1. This will help with step 5 – just trust me.
  4. Pull out the air filter cover, the actual filter, and its housing.
  5. Shut off or crimp the fuel valve and detach it from the carburettor. If you didn’t drain the fuel as detailed in step 3, you’ll find that fuel will get everywhere during this step.
  6. Remove the choke and throttle links from the carburettor throttle.
  7. Pull the carburettor from the mounting bolts.
    1. You may need to unthread a screw to release the carburettor bowl, though not all mowers have one.
  8. Remove the float pin, releasing the float pin and needle.
  9. Disassemble your carburettor.
    1. This may involve unthreading screws attached to your primer bulb and base, as well as a metering plate, gasket(s) and/or diaphragms, depending on your specific mower.
  10. Using carburettor cleaner or WD-40, spray the carburettor intake and outlet, wiping it down with a dry rag.
    1. Repeat on the carburettor bowl if you have one.
  11. Sand any corroding spots inside the carburettor with a fine-grit sandpaper.
  12. Once all of the bits and bobs are clean and dry (very important) reassemble everything in reverse order.

And that’s that! While the process will vary somewhat by your model and manufacturer, this is a solid guide to get you started. And, if you’re a visual learner like me, here’s a handy video.

How Long Should a Petrol Lawn Mower Last?

This is one of those questions that will vary based on the model and manufacturer of your lawn mower and, more importantly, how well you take care of it. I’ve seen lawn mowers last longer than the family dog, and I’ve seen ones that died within months of purchase. However, there is a general rule of thumb for the average lifespan of a petrol lawnmower.

The average petrol lawn mower lasts roughly ten years, varying on how well it’s maintained.

How Much is a Petrol Lawn Mower Service?

This will vary based on where you live, how in-demand lawn mower service is, and a number of other factors.

However, the general range is between £50-£500. This may seem like a massive range, and it is! That’s because it all depends on what you need serviced, how intensive the process is, how expensive the part(s) will be, and the cost of labour, among many other things.

For example, a basic motor repair can be as cheap as £20, but the labour will add an additional ~£30, whereas a full tuneup and servicing (let alone an engine rebuild) can be upwards of £500 after parts and labour are accounted for.

Where is the Air Filter on a Petrol Lawn Mower?

While this will vary somewhat based upon the model and manufacturer of your mower (are you tired of reading that? Because I’m tired of writing it.) among other things.

Generally, though, the air filter for a petrol lawn mower is located at the top of the engine. It will usually be encased in a metal or plastic shield secured with screws or snap fittings.

How Do I Clean the Air Filter on My Petrol Mower?

As per usual, this is a general guide that will vary based on your lawn mower’s model and manufacturer. Here’s what to do:

  1. Ensure the mower is off and cooled. As per usual, don’t clean a hot mower – you will get burned.
  2. Remove the spark plug.
  3. Disconnect the air filter’s shroud (generally at the top of the mower’s engine).
    1. This is usually held in place with standard Phillip’s head screws or snap fittings.
  4. Remove and inspect the filter:
    1. Paper filter:
      1. Gently tap it to remove excess buildup and hold it to a light source. If you can’t see through it (or struggle to), replace it. Do not try to clean paper filters, as they’ll fall apart.
    2. Foam filter:
      1. If the filter is crumbling, dark brown, or dark yellow – replace it. If not, clean it.
    3. Hybrid filter:
      1. Follow your manufacturer’s guidelines. Hybrid air filters are generally designed with a specific cleaning method/product in mind, and ignoring that could damage the filter. If the filter is stiff, heavily stained, or brittle, replace it.
  5. Assuming the filter isn’t paper, run the filter under water in a sink or with a hose outside. Use a gentle dish detergent (such as Dawn), rinse the filter, and squeeze out excess water and soap until it comes back clean.
    1. Some experts recommend oiling your filter, while others claim that it will damage your filter. My advice is to check your manufacturer’s guidelines and follow them to the tee.
    2. Allow the filter to dry fully before returning it to its housing to prevent mould or mildew buildup.
  6. Clean the housing of your air filter with a dry rag and replace all of the parts in reverse order
  7. Success!

And there you go – how to clean a petrol mower’s air filter in 7 easy steps!

Do I Need to Put Oil in My Petrol Lawn Mower?

Petrol lawn mower inspection

If your lawnmower has an internal combustion engine (spoiler: if it’s petrol, it does), you need to put oil in it regularly, just like your car. This oil lubricates the numerous moving parts of the engine and keeps them from getting damaged over time.

Check your lawn mower’s oil levels every time you finish mowing just as you would the oil of your car (with a dipstick) and top it off as needed, changing it every time you service the mower (generally once to twice per year).

How Much Oil To Put in a Petrol Lawn Mower?

This varies somewhat by the make and model of your mower, but generally, you’ll need between 400-600 mL of oil for a petrol (push) lawn mower, while a riding mower will generally take between 1-2 litres of oil.

(That’s 20-24 fluid ounces of oil for a push mower and 33-66 fluid ounces of oil for a riding lawn mower for you Yanks in the readership.)

What Oil Does a Petrol Lawn Mower Take?

red jerrycan

Lawn mower oil, surprisingly, comes in a number of various forms. The most common ones are as follows:

  • Single-Grade Oil: This comes with no additives (generally added to change viscosity) and will stay the same consistency in temperatures up to 100°C.
  • Multi-Grade Oil: This uses additives to control viscosity at higher temperatures.
  • Synthetic Blend Oil: This is a mix of the former two with additives to help it in cold temperatures without being as expensive as full synthetic oil.
  • Full Synthetic Oil: Full synthetic oil is both the most expensive and the most adaptable to various performance/commercial engines and in numerous temperatures.

But which one is right for your mower? I’m so glad you asked!

Some lawn mower engines are two-stroke engines, while others are four-stroke engines. The former is the older model and a bit less common, while the latter is becoming increasingly common. The best way to tell which type your engine falls under is to read your owner’s manual (I know, *groan* reading).

The oil that’s best for your lawn mower is generally just as simple as finding the highest-quality two or four-stroke oil. Car engine oil is entirely acceptable, though some experts insist that small-engine oil specifically will improve the lifespan of your lawn mower. It’s worth noting that I’ve found no hard-and-fast confirmation of that claim, though.

To mix your oil (that’s what 2-stroke is, oil mixed with fuel) simply add the requisite amount of oil to an empty Jerrycan and fill the can the rest of the way with petrol.

How Do I Tell if My Lawnmower is 2 or 4-Stroke?

There are two ways to check if your lawn mower is 2 or 4-stroke:

  1. Check your user manual.
    1. This is self-explanatory but boring.
  2. Inspect your engine.
    1. 2-stroke engines have one fuel intake/port, whereas 4-stroke engines have two intakes.

Experienced users can also tell by the engine sound (2-stroke is generally loud and high-pitched, whereas 4-stroke are quieter and low-pitched) or exhaust (2-stroke is less efficient, 4-stroke is more environmentally friendly and efficient).


All in all, petrol lawn mowers are simultaneously highly complicated machines and surprisingly simple to maintain. It takes a couple of hours once (maybe twice) a year, and you’ll have a mower that lasts for easily a decade, if not outliving some of your favourite tools! Just be sure to regularly check all of the moving parts, sharpen the blades as needed, and pick the proper oil and you’re all set.

Now sit back, make a drink, and relax – you’ve earned it.