E0 is gasoline with zero ethanol, and E10 is gasoline blended with 10% ethanol by volume. E10 is the standard fuel sold at most gas stations in the United States today, while E0 (sometimes labeled “ethanol-free” or “recreational fuel”) is a specialty product typically found at select stations, marinas, and hardware stores. The difference between them matters most for fuel economy, engine compatibility, and storage life.
What’s in Each Blend
E0 is pure petroleum gasoline with no ethanol mixed in. E10 contains 90% gasoline and 10% ethanol, an alcohol derived from corn or other plant material. The “E” stands for ethanol, and the number tells you the percentage. You may also see E15 (15% ethanol, approved for vehicles from model year 2001 and newer) and E85 (up to 83% ethanol, only for flex-fuel vehicles) at some pumps.
E10 became the default blend largely because of federal renewable fuel mandates. The EPA sets annual biofuel volume requirements under the Renewable Fuel Standard, and for 2025 the total renewable fuel target is 22.33 billion ethanol-equivalent gallons. That policy is the reason nearly all regular unleaded gasoline now contains ethanol.
Octane, Energy, and Fuel Economy
Ethanol has a high octane rating, which is why refiners use it as an octane booster. Adding ethanol lets them reduce the proportion of aromatic hydrocarbons (chemicals that contribute to soot and particulate emissions) while still hitting the 87-octane mark for regular fuel. So E10 achieves its octane rating partly through ethanol rather than relying entirely on petroleum chemistry.
The tradeoff is energy. Ethanol contains significantly less energy per gallon than gasoline. Pure ethanol (E100) holds only about 76,330 BTUs per gallon, roughly 67% of the energy in a gallon of gasoline. E10 lands in the range of 112,114 to 116,090 BTUs per gallon, compared to slightly higher figures for pure gasoline. In practical terms, the U.S. Energy Information Administration estimates that E10 reduces fuel economy by about 3% compared to ethanol-free gasoline. On a 30 MPG car, that works out to losing roughly 1 mile per gallon.
Why E0 Still Exists
If E10 is the standard, why does anyone bother selling ethanol-free gas? The answer comes down to small engines, boats, and storage. E0 is marketed as “recreational fuel” or “rec gas” because it’s better suited for equipment that sits idle between uses or operates in wet environments.
Ethanol is hygroscopic, meaning it pulls moisture from the air. In a fuel tank, ethanol would rather bond with water than stay dissolved in gasoline. If enough moisture accumulates, the ethanol-water mixture separates from the gasoline and sinks to the bottom of the tank. This is called phase separation, and it can cause an engine to stall or refuse to start because it’s trying to burn a water-alcohol mix instead of fuel.
Phase separation is a minor concern for daily drivers that burn through a tank of gas every week or two. It becomes a real problem for lawnmowers stored over winter, chainsaws that sit in a garage for months, generators kept for emergencies, and boats exposed to humid air near water.
Small Engine Risks With E10
Beyond water absorption, E10 is more corrosive than pure gasoline. Over time it can degrade rubber seals, hoses, and gaskets in fuel systems that weren’t designed for ethanol exposure. Older small engines are particularly vulnerable because their fuel system materials predate the widespread adoption of ethanol blends.
E10 also tends to leave deposits as it interacts with fuel system components, and those deposits clog carburetors and fuel lines. A snowblower left with E10 in the tank for 12 months, for example, can end up needing a full carburetor rebuild before it will run again. This is why many equipment manufacturers recommend either using ethanol-free fuel or adding a fuel stabilizer before storing any gas-powered tool for more than 30 days.
Modern cars handle E10 without issue. Vehicles manufactured after 2000 are generally designed for ethanol-blended fuel, and their fuel systems use materials resistant to ethanol corrosion. If you drive a car from the last two decades, E10 is perfectly fine for everyday use.
Storage and Shelf Life
E0 lasts longer in storage because there’s no ethanol to attract moisture or degrade. In a sealed container kept in a cool, dry place, ethanol-free gasoline can remain usable for a year or more without stabilizer. E10 is more unpredictable. In sealed containers stored indoors, some people report it lasting six months to two years without problems. But in a vented fuel tank exposed to temperature swings and humidity, E10 can go bad in as little as three to six months.
The safest guideline: if E10 will sit unused for more than 60 to 90 days, either drain the fuel system, add a stabilizer, or switch to E0. For emergency generators and seasonal equipment, keeping a supply of ethanol-free gas eliminates the most common cause of “it won’t start when I need it.”
Cost and Availability
E0 typically costs 30 to 75 cents more per gallon than E10, depending on your region. The premium reflects both lower demand and the fact that refiners produce it outside the standard ethanol-blended supply chain. You can find E0 at dedicated pumps in some gas stations (often labeled “no ethanol” or “recreational fuel”), at marinas, and through online station locators like pure-gas.org that map ethanol-free retailers by state.
For most drivers filling up a car, E10 is the practical and economical choice. The 3% fuel economy difference doesn’t justify paying a significant per-gallon premium. But for anyone fueling boats, storing gas for emergencies, or running small engines seasonally, E0 solves a set of real problems that make the higher price worthwhile.