A Guide to Storing Fuel for Your Lawn Mower

Knowing how to store lawn mower fuel correctly is a crucial part of seasonal equipment care. Improperly stored gasoline can degrade, leading to frustrating starting problems, poor engine performance, and even damage to your mower’s carburetor and fuel system. By following a few key practices—using the right container, adding a stabilizer, and choosing the proper location—you can protect your fuel’s quality and ensure your mower is ready to go when you need it. This guide walks you through the essentials of safe fuel storage, tying into the broader steps outlined in our seasonal mower maintenance routine.

Why Proper Fuel Storage Matters

Gasoline begins to degrade the moment it leaves the refinery. Two main processes work against it: oxidation and evaporation. Oxidation occurs when fuel reacts with oxygen, forming gums and varnishes that can clog the tiny passages in your mower’s carburetor and fuel injectors. Evaporation causes the lighter, more volatile components of gasoline to escape, leaving behind a thicker, less combustible fuel that is harder to ignite. In engines not designed for it, ethanol-blended fuels can absorb moisture from the air (a process called phase separation), leading to a corrosive mixture that damages fuel system components. Proper storage slows these processes, preserving fuel quality and protecting your engine investment.

Choosing the Right Fuel Container

The container is your first line of defense in preserving fuel. Using an old milk jug or unapproved plastic bottle is dangerous and ineffective.

The Role of Fuel Stabilizer

A fuel stabilizer is a chemical additive that slows the oxidation process and helps maintain the fuel’s combustibility. It’s highly recommended for any fuel you plan to store for more than 30 days, especially for seasonal equipment.

• How to Use It: Add the stabilizer to a fresh, full container of gasoline before storage, not to old, already-degraded fuel. Follow the product’s mixing instructions carefully—typically, you pour the recommended amount into the container, then add the gasoline. This ensures it mixes thoroughly as you fill.
• When to Use It: The best practice is to add stabilizer to every gallon you purchase for your small engines. This way, whether the fuel goes into the mower immediately or sits in the can for a few weeks, it’s already protected.
• For the Mower Itself: As part of your lawn mower winter storage procedure, you should run the engine for a few minutes after adding stabilized fuel to the tank. This circulates the treated fuel through the carburetor and fuel lines, protecting the entire system.

Avoiding Ethanol-Blended Fuels (E10)

Most gasoline sold at pumps contains up to 10% ethanol (E10). While fine for most modern cars, ethanol can cause problems in small engines during storage.

If you must use E10, a stabilizer formulated to handle ethanol is critical. For the longest storage life and greatest engine protection, seeking out ethanol-free fuel is the best choice.

How to Store Lawn Mower Fuel: Step-by-Step

1. Start with Fresh Fuel: Purchase only the amount of gasoline you expect to use within your storage timeframe.
2. Add Stabilizer Immediately: In your approved, clean container, add the correct dose of fuel stabilizer first.
3. Fill the Container: Add gasoline to the container, filling only to the container’s fill line so there is room for the fuel to expand.
4. Seal and Label Tightly: Secure the cap firmly. Label the container with the fuel type and purchase date.
5. Choose a Safe Storage Location: Store in a cool, dry, well-ventilated place out of direct sunlight and away from living areas. A detached, ventilated shed or garage is ideal. The location must be away from pilot lights, furnaces, water heaters, or any other ignition source.
6. Keep Out of Reach: Ensure stored fuel is inaccessible to children and pets.

How Long Can You Store Gasoline?

Storage duration depends heavily on whether the fuel is treated and the type of container used.

• Untreated Fuel (E10): Can begin to degrade in as little as 30 days. Performance issues are likely after 3-6 months.
• Treated Fuel (with Stabilizer): Properly stabilized gasoline in a sealed, approved container can stay usable for as long as the stabilizer’s label states.
• Best Practice: For seasonal mower use, we recommend a “one season” rule. Purchase fresh fuel in the spring, treat it with stabilizer, use it over the mowing season, and properly dispose of any leftover fuel at season’s end before your winter storage routine. This cycle ensures you always have fresh fuel on hand.

When you’re ready to mow again, checking and potentially replacing old fuel is a key step in your lawn mower spring preparation.

Disposing of Old Gasoline

If fuel is old, contaminated with dirt or water, or has a sour smell, do not use it in your mower. Do not pour it on the ground, down a drain, or into the trash.

• Check Local Resources: Contact your local household hazardous waste (HHW) collection facility or fire department for disposal guidelines. Many communities have specific collection days or permanent drop-off sites.
• Use a Transfer Container: Take old fuel to the disposal site in its original, properly labeled container, or transfer it carefully to a container you can dedicate for disposal.

FAQ

Can I store gas over winter for my mower?

Yes, you can store gasoline over winter, but it must be done correctly. Use an approved container, fill it nearly full, add a fuel stabilizer immediately after purchase, and store it in a cool, dry, well-ventilated location away from any heat source or living space. This stored fuel can then be used to fill your mower in the spring, or to mix with fresh fuel.

Does fuel go bad in a sealed container?

Yes, even in a sealed container, fuel will eventually degrade through oxidation. A sealed, metal container offers the best protection, but plastic containers are permeable to some extent, allowing slow vapor loss and air exchange. Using a stabilizer and limiting storage time are necessary regardless of container type.

Should I drain the gas from my mower for storage?

The recommended method depends on the storage length and your mower type. For long-term seasonal storage (like over winter), the best practice is to add stabilizer to fresh fuel, run the engine to circulate it, then top off the tank. This protects the entire fuel system. For some equipment, manufacturers may recommend draining the carburetor bowl. Always consult your mower’s manual for its specific storage instructions, which you can find as part of our general lawn mower maintenance advice.

What’s the difference between fuel stabilizer and fuel treatment?

The terms are often used interchangeably, but “stabilizer” typically refers to additives whose primary function is to prevent oxidation and extend shelf life for storage. “Fuel treatment” is a broader term that may include stabilizers but can also contain cleaners designed to remove existing deposits from the fuel system during normal operation. For storage purposes, you want a product labeled as a stabilizer.

How does fuel storage relate to summer mower care?

During the active mowing season, it’s wise to manage your fuel supply to avoid using degraded gas. Buying fuel in smaller quantities, adding stabilizer to your storage can, and using it within a few months helps maintain performance. This practice prevents problems related to old fuel, which is a common summer issue. For more tips, see our guide on essential summer lawn mower care.