The choice of gasoline for a lawn mower or other small, air-cooled engine significantly impacts its performance and longevity. Modern fuel blends, common at most stations, differ substantially from the pure gasoline older equipment was designed to use. Understanding the difference between E0 and E10 gasoline is necessary to protect your equipment. This difference relates primarily to the inclusion of ethanol, an alcohol-based additive.
Understanding E0 and E10 Fuel Types
The labels E0 and E10 refer to the maximum percentage of ethanol blended into the gasoline by volume. The “E” stands for ethanol, and the corresponding number indicates the maximum amount of this additive present in the fuel mixture. This terminology provides a quick way to identify the fuel composition at the pump.
E0 gasoline is pure, unleaded gasoline that contains no ethanol. This fuel is often called non-oxygenated gasoline and is the formulation most older small engines were designed to use. E10 gasoline is a blend of 90% unleaded gasoline and up to 10% ethanol. This blend is now the standard grade of fuel available at most automotive filling stations.
Ethanol’s Effect on Small Engine Components
The inclusion of ethanol in E10 fuel introduces several challenges for the fuel systems of small engines, which are generally less robust than those in modern automobiles. One of the most significant issues is ethanol’s hygroscopic nature, meaning it readily attracts and absorbs moisture from the surrounding air. This water absorption can lead to a process called phase separation, where the water and ethanol separate from the gasoline and sink to the bottom of the fuel tank.
The separated water-ethanol layer is highly corrosive and causes rust and deterioration of metal parts inside the fuel tank, fuel lines, and carburetor bowl. Since small engines are often used seasonally and stored for long periods, this sitting mixture causes significant damage. The corrosion is accelerated, especially in parts made from aluminum or magnesium.
Ethanol also acts as a powerful solvent, which can degrade certain materials found in older fuel systems. It can cause older rubber hoses, gaskets, and plastic components to swell, crack, or become brittle, leading to leaks or component failure. Ethanol can also loosen accumulated varnish and gum deposits from the fuel tank and lines. These dislodged particles then travel through the system and clog the small passages and jets within the carburetor, resulting in poor engine performance.
Fueling Recommendations for Lawn Mowers
For maximum engine protection and reliability, particularly for equipment that sits unused for extended periods, E0 (non-ethanol) gasoline is the preferred fuel choice. E0 does not absorb moisture, nor does it possess the solvent properties that break down fuel system components or dislodge deposits. Using this fuel ensures that the gasoline remains stable for a longer duration, reducing the risk of corrosion and carburetor clogging during off-season storage.
If E10 gasoline must be used, employ certain mitigation strategies to protect the engine. The fuel should be purchased in small quantities that can be consumed within 30 days to prevent it from going stale. A high-quality fuel stabilizer, specifically formulated to address ethanol issues, should always be added.
Before any extended storage period, the small engine’s fuel system should be completely drained. This is accomplished by running the engine until it stops from lack of fuel, ensuring the carburetor bowl is empty and preventing phase separation. While many current engine manufacturers approve the use of E10, checking the owner’s manual for specific recommendations remains the best practice. E0 fuel is generally found at specialized stations, such as marinas, or can be purchased in pre-mixed, canned formats designed for small engines.