Disposing of old gasoline from a lawn mower is necessary because it is classified as hazardous waste. Stale gasoline has degraded over time, losing its volatile components and forming gummy, varnish-like residues. Because of its flammability and toxicity, gasoline cannot be poured down storm drains, thrown into the regular trash, or dumped onto the soil, as this poses significant environmental contamination and fire hazards. Proper disposal protects local ecosystems, prevents water source contamination, and avoids potential legal penalties.
Recognizing Fuel That Needs Disposal
Gasoline begins to degrade when exposed to oxygen, a process called oxidation, which chemically changes the hydrocarbons in the fuel. Standard unleaded gasoline, especially the type containing ethanol, becomes unstable and loses its effectiveness after just three to six months if not stabilized. The lighter, more volatile compounds evaporate first, leaving behind a heavier mixture that does not combust properly, leading to engine sputtering, difficulty starting, or failure to run.
You can identify stale fuel by its distinct appearance and smell. Degraded fuel often looks darker, cloudier, or yellower than new, clear fuel. Oxidation results in a sour, varnish-like, or acidic odor, which is much stronger than the familiar smell of fresh gas. If you also notice sediment, rust, or gummy deposits floating in the fuel, it is contaminated and should not be used.
Safe Collection and Temporary Storage
Handling and draining old fuel requires safety precautions. Always work outdoors in a well-ventilated area, and wear protective gloves and eye protection. To drain the fuel from your lawn mower, you can use a siphon pump or a turkey baster to remove the gas directly from the tank.
Alternatively, you may disconnect the fuel line from the carburetor to allow the fuel to empty into a receptacle. The collected fuel must be immediately transferred to a certified container approved for gasoline storage. These containers are sealed, heavy-duty plastic or metal and should be filled no more than 95% to allow room for vapor expansion. Label the container “Old Gasoline” and store it upright in a cool, dry location away from heat sources, sparks, or ignition sources.
Official Disposal Channels
Old gasoline is Household Hazardous Waste (HHW) and must be disposed of through regulated channels. The most common and legally compliant destination is a local HHW collection facility or a municipal transfer station. These sites are equipped to handle, treat, and recycle flammable liquids and can be located by searching your city or county’s waste management website.
Contact the facility beforehand, as some collection sites operate on specific schedules, require appointments, or have volume limits for the amount of fuel they will accept. Specialized automotive recycling centers or some local auto repair shops may also accept old gasoline for proper disposal or blending. If you have a two-stroke engine, the gas is mixed with oil, and while HHW sites accept this mixture, it must be kept separate from pure gasoline in its own labeled container.
Strategies for Minimizing Fuel Waste
The most effective way to manage old gasoline is to prevent it from going stale. Purchase only the amount of fuel you anticipate using within a short period, ideally within two to three months. For seasonal storage, using a quality fuel stabilizer is effective, as it slows the degradation of the gasoline and prevents gum and varnish from forming in the fuel system.
The stabilizer should be added to fresh gasoline in the storage container immediately upon purchase, and the engine should be run for several minutes to circulate the treated fuel. Stabilized fuel can remain fresh for up to one to three years, eliminating the need to drain the tank at the end of the season. Storing gasoline in a cool, dark, and dry location will further maximize its shelf life by reducing the effects of heat and humidity.