How Often Should You Service a Petrol Mower or Strimmer?

As a general rule, a petrol lawnmower or strimmer used for a typical UK garden should get a full service once a year, usually at the start of the growing season in spring, plus a few quick checks every few uses in between. Equipment used heavily — for a large garden, multiple properties, or trade use — may need attention every 25-50 hours of running time instead of just once a year.

What an annual service actually covers

A proper service isn't just a wipe-down. For a typical petrol mower or strimmer, it usually includes:

• Air filter: cleaned or replaced — a clogged air filter is one of the most common causes of a machine that won't start or runs rough.
• Spark plug: cleaned, gapped correctly, or replaced if worn. A tired spark plug causes hard starting and poor running.
• Oil change (four-stroke engines): old oil breaks down and loses its ability to protect the engine.
• Fuel system check: old fuel left in the tank or carburettor over winter is one of the single biggest causes of spring starting problems — draining and refreshing fuel, and cleaning the carburettor if needed, sorts this.
• Blade or line-head: sharpened or replaced (mower blades), and general cutting mechanism checked for wear or damage.
• General safety check: guards, handles, cables and the kill switch/safety interlock all working properly.

Typical cost

A basic service from a local small-engine specialist or garden machinery dealer typically costs somewhere in the region of £40-£80 for a domestic mower or strimmer, depending on what's needed — a full service with parts (air filter, spark plug, oil) tends to sit toward the top of that range.

What you can reasonably do yourself

Cleaning debris off the machine after each use, checking the air filter isn't visibly clogged, and making sure there's no old fuel sitting in the tank over winter are all realistic DIY tasks that don't need special tools. Sharpening or replacing a strimmer's cutting line is also a straightforward DIY job. Blade sharpening, carburettor work, and anything involving the ignition system is usually better left to a specialist, both for safety and because getting it wrong can cause a much more expensive repair.

Signs your equipment needs attention now, not at the next scheduled service

• Hard to start, or needs several pulls where it used to start on the first or second.
• Running rough, stalling, or losing power under light load.
• Visible fuel smell or leaking fuel.
• Unusual vibration or noise from the cutting mechanism.

If you're only using a strimmer for one job — clearing an overgrown area before a bigger garden project, for example — it's often more cost-effective to hire a strimmer for the day rather than buy and maintain one you'll rarely use.

Common mistakes

• Leaving fuel in the tank over winter. Petrol degrades over a few months and can gum up the carburettor — either run the tank dry before storage or use a fuel stabiliser.
• Ignoring a clogged air filter. It's a five-minute check that prevents a huge share of common starting problems.
• Storing equipment outdoors uncovered. Damp and temperature swings accelerate wear on cables, seals and the ignition system.

Two-stroke vs four-stroke engines

Many strimmers and some smaller mowers use a two-stroke engine, which runs on a petrol-and-oil mix rather than petrol alone — getting this mix wrong (too little oil starves the engine of lubrication; too much fouls the spark plug and causes smoky, rough running) is a very common cause of premature engine wear. Most mowers use a four-stroke engine instead, with separate petrol and oil, closer to a car engine in principle, which is why they need a proper oil change as part of servicing rather than just a fuel top-up. If you're not sure which your machine has, check the handbook — running the wrong fuel type is one of the most damaging (and easily avoidable) mistakes owners make.

If you only need equipment occasionally, remember that hiring specialist garden equipment for a single job avoids the ongoing servicing and storage question altogether.

Where to get equipment serviced

Most UK towns have at least one independent small-engine or garden machinery specialist, and many garden centres offer a servicing drop-off too. Booking ahead of the spring rush (February-March) tends to get a quicker turnaround than waiting until everyone else has the same idea in April. If you bought the machine from a specific dealer, they'll often service the same brand and may have manufacturer-specific parts on hand, which can be quicker than a generalist.