How do you drain the gas from a lawn mower?
Draining the gas from a lawn mower is a simple job you do before storage, an oil change, or transport, and there are two safe ways to do it. Always work outdoors on a cool engine, well away from any flame, cigarette, or spark, and wear gloves and eye protection, because petrol vapour ignites easily and is harmful to skin and lungs.The steps below cover the most reliable method, siphoning, followed by the run-dry alternative.
- Move the mower outdoors onto a level surface and let the engine cool completely.
- Place an approved petrol container below the level of the fuel tank.
- Insert a hand-pump siphon or fuel-transfer pump into the tank and pump the petrol into the container.
- Tilt the mower slightly toward the siphon, keeping the air filter and spark plug side up, to draw out the last of the fuel.
- For any fuel you cannot siphon, start the engine in a clear area and let it run until it stops on its own.
Disconnecting the spark plug wire before you tilt or work near the deck is a sensible extra precaution, so the engine cannot start unexpectedly.
Why drain the gas at all?
Draining the gas matters because petrol left standing for months is the single most common reason a mower will not start again. As fuel ages, the ethanol blended into most pump petrol absorbs moisture and the fuel forms gums and varnish that clog the tiny jets inside the carburettor.A clogged carburettor is a fiddly, sometimes costly repair, whereas an empty or stabilised tank costs nothing to arrange. Draining also makes the mower safer and lighter to transport in a car, and it is the sensible first step before tipping the mower for an oil change or a blade swap, since a full tank can leak fuel into the air filter when the machine is on its side.
Siphon or run-dry: which method is better?
Siphoning is the better method when you want to save the fuel, while running the engine dry is simplest when the tank is nearly empty already. Siphoning removes almost all the petrol cleanly, but a little always remains in the carburettor bowl.For long-term storage the two methods are often combined: siphon the bulk of the fuel out of the tank, then start the engine and let it run until it stalls, which burns off what is left in the carburettor. That leaves nothing behind to turn to varnish over winter. If you only need to lower the fuel level for transport, siphoning alone is enough, and there is no need to run the engine dry.
What if you want to keep the fuel instead?
Fresh petrol you have just drained is fine to reuse, provided it is clean and less than about a month old, so pour it back into the tank for the next mow or into another petrol tool. Old, cloudy, or water-contaminated fuel should not go back in.A worked example makes the choice clear. Suppose you are draining a mower in autumn that you filled a fortnight ago with fresh E10: that fuel is still good, so siphon it into a clean can, store the can somewhere cool, and use it within the month. If instead the tank holds petrol of unknown age that has sat all summer, treat it as waste and take it to a household hazardous-waste facility rather than risk gumming up the next engine you pour it into. Never tip old petrol down a drain, onto soil, or into household rubbish.
A few final safety points
Handle every step outdoors, keep a clear space around you, and never drain or store petrol near a water heater, boiler, or anything with a pilot flame. Petrol vapour is heavier than air and travels along the ground to find an ignition source.Keep a suitable fire extinguisher within reach, wipe up any spills at once, and let rags dry outdoors before disposal rather than bundling fuel-soaked cloth into a bin. Our lawn mower maintenance guide covers the wider seasonal service that draining the fuel is usually part of. Fuel handling carries real fire risk, so treat this as general guidance and always follow the procedure printed in your mower's manual.
