How To Drain The Gas From A Lawn Mower

Learning how to drain the gas from a lawn mower is a key piece of seasonal maintenance. Safely draining the gasoline from your lawn mower prevents stale fuel from causing starting issues next spring. Old gas can gum up the carburetor and fuel lines, leading to frustrating repairs. This guide will walk you through the simple process, ensuring your mower is stored properly and ready to run when you need it.

There are a few common methods for removing fuel, and the best one depends on your mower’s design. The main approaches are siphoning the gas from the tank, running the engine until the carburetor is empty, or using a fuel shut-off valve if your model has one. You’ll need some basic tools and a safe place to work. Always perform this task in a well-ventilated area, away from any open flames or sparks.

Tools And Materials You Will Need

Gathering your supplies before you start makes the job quicker and safer. You likely have most of these items already in your garage or shed.

A safe fuel container approved for gasoline storage
A length of clear plastic tubing for siphoning (about 3-4 feet)
A socket set or wrench to remove the fuel line or tank
A flat-head screwdriver
Protective gloves and safety glasses
An old rag or a bundle of paper towels
A small funnel
A baking pan or tray to catch any drips

Safety Precautions Before You Begin

Gasoline is highly flammable and its fumes are dangerous. Never overlook these critical safety steps.

Work outdoors in a open, well-ventilated area. Never in a basement or enclosed space.
Ensure the lawn mower engine is completely cool to the touch before starting.
Disconnect the spark plug wire to prevent any accidental ignition.
Have a fire extinguisher rated for flammable liquids nearby.
Do not smoke or work near pilot lights, electrical tools, or anything that could create a spark.
Place the mower on a flat, stable surface to prevent tipping.

Choosing The Right Fuel Container

It is essential to use a container designed for gasoline. Look for a red plastic can with a UL or FM approval label. These containers are built to safely handle the fumes and pressure changes. Never use a milk jug, glass bottle, or any container not meant for fuel. You will need this container to hold the old gas you drain, which should be disposed of properly at a hazardous waste facility.

Method One: Siphoning The Gasoline

Siphoning is often the most straightforward method, especially for mowers with a large fuel tank. This technique physically removes almost all of the liquid fuel.

Position your approved gas can on the ground, lower than the mower’s fuel tank.
Insert one end of your clear tubing deep into the mower’s gas tank.
Place the other end of the tube in your mouth and give a quick, gentle suck until you feel the gasoline begin to flow. Immediately direct this end into the gas can. Alternatively, you can use a manual pump siphon from an auto parts store to avoid using your mouth.
Allow the tank to drain completely into the container.
Once the flow stops, carefully remove the tube, letting any residual gas drip into the can.
Use your rag to wipe up any spills around the fuel tank cap area.

Method Two: Running The Engine Dry

This method is common for end-of-season storage and involves using up the fuel that’s in the carburetor. It doesn’t drain the main tank, so it’s often combined with siphoning for a complete job.

First, siphon or drain the bulk of the fuel from the main tank using Method One.
Reconnect the spark plug wire if you disconnected it earlier.
Move the mower to an open area and start the engine. It may run rough as it uses the last of the fuel in the system.
Let the engine run until it sputters and stops on its own. This indicates the carburetor bowl is empty.
Once the engine is completely stopped, disconnect the spark plug wire again for safety.
Attempt to restart the engine once or twice to confirm no fuel remains in the carburetor. This helps ensure it’s truly empty.

When Not To Use The Run-Dry Method

Do not use this method on lawn mowers with electronic fuel injection or if the engine has a fuel pump. Running these systems dry can cause damage. Always check your owner’s manual for the manufacturer’s specific storage instructions. Also, avoid this if you have added a fuel stabilizer, as the goal then is to keep treated fuel in the system.

Method Three: Using The Fuel Shut-Off Valve

Some older or more commercial-style mowers have a small valve on the fuel line between the tank and the carburetor. This provides a very clean way to drain the carburetor bowl.

Place your drip pan or tray under the carburetor area.
Locate the fuel shut-off valve on the fuel line and turn it to the “Off” position.
Find the drain screw or nut on the bottom of the carburetor bowl. It is often a small brass fitting.
Loosen this screw with a wrench or screwdriver, allowing the fuel from the carburetor bowl to drain into your pan.
Once it’s fully drained, tighten the drain screw securely.
You can then siphon the remaining fuel from the main tank as described in Method One.

What To Do With The Drained Gasoline

You should never pour old gasoline down a drain, onto the ground, or into regular trash. Proper disposal is a must.

If the gasoline is relatively fresh (less than a month old) and uncontaminated, you can reuse it in your car’s gas tank by mixing it with a full tank of fresh fuel. Do not use fuel that has been mixed with 2-cycle oil.
For old, stale, or contaminated gas, take it to a local hazardous waste disposal facility, an automotive repair shop that accepts it, or a community hazardous waste collection event. Check with your local government for locations.
Store the gas in its approved container with the lid tightly sealed until you can dispose of it.

Preparing Your Mower For Long-Term Storage

Draining the gas is just one part of preparing your mower for the off-season. Following these additional steps will keep it in top condition.

After draining the fuel, consider adding a teaspoon of fresh oil into the spark plug hole and pulling the starter cord a few times to coat the cylinder walls.
Clean the mower deck thoroughly of all grass clippings and debris to prevent rust.
Sharpen or replace the mower blade so it’s ready for next season.
Check the air filter and replace it if it’s dirty.
Store the mower in a clean, dry place, preferably covered with a breathable cloth.

The Fuel Stabilizer Alternative

For many people, using a fuel stabilizer is easier than draining the tank. This is a chemical additive that prevents fuel from breaking down and varnishing for up to 24 months.

Add the correct amount of fuel stabilizer to a nearly full gas tank.
Run the engine for 5-10 minutes to circulate the treated fuel throughout the entire fuel system, including the carburetor.
Turn off the engine and let the mower cool.
Proceed with your other storage steps. The stabilized fuel will remain inside the tank and carburetor all winter.

This method is highly effective and recommended by many manufacturers. It saves you the step of disposing of old gas, but you must remember to add the stabilizer before the fuel goes stale.

Common Problems And Troubleshooting

Sometimes, things don’t go exactly as planned. Here are solutions to a few common issues.

Gas Tank Has A Screen Or Built-In Spout

Some tanks have a anti-siphon screen. If your tube won’t go in, you may need to remove the fuel line from the bottom of the tank or use the fuel shut-off valve method. For tanks with a spout, you can often tip the mower carefully (spark plug side up) to pour the fuel out directly into a can.

Fuel Line Is Brittle Or Cracked

If the fuel line cracks when you touch it, it needs to be replaced. This is a good opportunity to install a new line. Note the routing of the old line, cut a new piece of fuel-rated hose to length, and attach it with new clamps.

Drain Screw Is Stripped Or Stuck

Do not force a stripped drain screw. Applying heat carefully with a hairdryer can sometimes expand the metal and loosen it. If it’s truly stuck, you may need to take the carburetor to a small engine repair shop to avoid causing major damage.

Frequently Asked Questions

Here are answers to some common questions about draining lawn mower gas.

How Often Should I Drain The Gas From My Lawn Mower?

You should drain or stabilize the gas whenever you plan to store the mower for more than 30 days. This is especially critical for seasonal storage over winter. For regular use, try to use fresh gas within a month of purchase.

Can I Leave Gas In My Lawn Mower Over Winter?

It is not recommended to leave untreated gasoline in your mower over winter. The ethanol in modern gas attracts moisture and separates, leading to corrosion and gummy deposits that will clog your carburetor. Always either drain the fuel or use a stabilizer.

What Is The Easiest Way To Get Gas Out Of A Lawn Mower?

For most homeowners, using a fuel stabilizer is the easiest method. If you prefer to drain, siphoning with a manual pump siphon kit is very straightforward and keeps you from getting gas in your mouth.

How Long Does It Take For Gas To Go Bad In A Lawn Mower?

Gasoline can begin to degrade in as little as 30 days. Within 60-90 days, it often loses enough volatility to cause starting problems and leaves behind varnish and gum that clog fuel system components.

Will Old Gas Ruin A Lawn Mower Engine?

Yes, old gas is a leading cause of lawn mower failure. The gummy residues it leaves behind clog the tiny jets and passages in the carburetor, preventing the engine from getting the correct fuel mixture. This leads to hard starting, poor performance, or a complete failure to run.