How to Deal with Stale Fuel in your Lawn Mower

Stale fuel is one of the most common reasons a lawn mower refuses to start or runs poorly. If left sitting in the tank for too long, old petrol in a lawn mower can cause blockages, leading to rough running or complete failure to start. Many people face this issue after winter storage, and unfortunately, problems caused by lawn mower stale fuel are not typically covered under warranty. However, there are ways to fix this issue and prevent it from happening again.

How Does Stale Fuel Affect Your Lawn Mower?

Petrol starts to degrade after just a few weeks, especially when exposed to air. Over time, it becomes less effective, and residues can build up in the fuel system, particularly in the carburettor. This can cause your mower to “hunt” (run unevenly) or fail to start altogether. If you have left fuel sitting in the tank for months, the carburettor can become ‘gummed up,’ meaning it will need to be cleaned before the mower can run properly again.

How to Fix Stale Fuel in Your Lawn Mower

If you suspect stale fuel is causing your mower issues, follow these steps to try and get it running again:

1. Drain the Old Fuel from the Carburettor

The first step is to remove any old petrol in the lawn mower. The carburettor’s float bowl, located behind the air filter, holds fuel and can become clogged over time. To drain it:

• Locate the nut on the bottom of the float bowl and loosen it slightly.
• Allow the old fuel to drain completely from the machine.
• Dispose of the stale fuel properly and avoid letting it contaminate fresh petrol.

2. Clear Any Blockages in the Carburettor

Once the old fuel has been drained, you need to clear any blockages that may be affecting performance.

• Blow air through the fuel tank to help remove sediment in the carburettor.
• If available, use a carburettor cleaner spray to break down any deposits inside.
• For a more thorough clean, remove the float bowl and wipe out any crystallised petrol residue with a cloth or brush.

3. Refill with Fresh Petrol

After cleaning the carburettor, tighten the nut back onto the float bowl and refill your mower with fresh, high-quality fuel. This should help the engine run smoothly again.

If the mower still refuses to start after following these steps, it may require professional servicing. Keep in mind that fuel-related issues are not always covered under warranty, so regular maintenance is essential to prevent problems.

How to Prevent Stale Fuel Issues

To avoid dealing with stale fuel in your lawn mower, it’s important to take preventive measures:

• Use a Fuel Stabiliser – Adding a fuel stabiliser can extend the life of your petrol, reducing the chances of it going stale. Typically, 10ml of stabiliser is needed for every 10L of fuel for occasional use or 10ml for 3L if storing fuel for longer periods.

Find HONDA Fuel Stabiliser here.

• Empty the Fuel Tank Before Storage – If you know you won’t be using your lawn mower for a while, drain the fuel completely to prevent it from degrading inside the tank.
• Use High-Quality Fuel – Consider using premium fuel options like Aspen alkylate petrol, which lasts longer and burns cleaner, reducing the risk of carburettor blockages.

Keep Your Lawn Mower Running Smoothly

Old petrol in a lawn mower can cause frustrating issues, but with proper care and maintenance, you can avoid the hassle of stale fuel. By regularly using fresh petrol, adding a stabiliser, and ensuring your carburettor stays clean, you can keep your mower in top condition and ready to go when you need it.