E0 is gasoline with zero ethanol, pure petroleum fuel. E10 is gasoline blended with 10% ethanol by volume, making it 90% petroleum and 10% corn-based alcohol. E10 is the standard fuel sold at most gas stations across the United States today, so unless a pump specifically says “ethanol-free” or “pure gas,” you’re almost certainly buying E10.
The difference matters most for fuel economy, engine compatibility, and how long you can store the fuel before it goes bad. Here’s what you need to know about each.
How They Differ in Energy and Mileage
Ethanol contains less energy per gallon than pure gasoline. A gallon of E10 delivers roughly 97% of the energy found in a gallon of E0. In practical terms, the U.S. Energy Information Administration puts the fuel economy penalty at about 3% when using E10 compared to ethanol-free gas. For a car that gets 30 miles per gallon on E0, that works out to about 29 MPG on E10. Most drivers never notice the difference, but it adds up over a full tank: you’ll go slightly fewer miles before refueling.
E10 gasoline contains between 112,114 and 116,090 BTUs per gallon, according to the Department of Energy’s fuel comparison data. That range reflects the natural variation in gasoline formulations across refineries and seasons. E0 sits at the higher end of that spectrum since none of its energy content is diluted by ethanol.
Why E0 Is Preferred for Small Engines and Boats
The biggest practical reason people seek out E0 is to protect engines that sit idle for weeks or months at a time. Lawnmowers, chainsaws, generators, snowblowers, and boat engines all fall into this category.
Ethanol attracts and absorbs moisture from the air. In a car that burns through a tank every week or two, this isn’t a problem. But in a boat fuel tank or a snowblower sitting in the garage from March to November, that absorbed water can cause a process called phase separation. The ethanol and water bond together and sink to the bottom of the tank, creating a layer of corrosive liquid that sits right where the fuel pickup draws from. When you try to start the engine, it pulls in this water-ethanol mixture instead of usable fuel.
Ethanol also acts as a solvent. In older engines with cork gaskets or rubber fuel lines that weren’t designed for alcohol fuels, it can soften seals and accelerate their breakdown. In neglected fuel systems with years of built-up deposits, ethanol dissolves those deposits and sends them downstream into fuel filters and the tiny passages inside carburetors. This is the suspected main cause of most ethanol-related engine complaints. One forum user described forgetting about a snowblower stored for 12 months with E10 in the tank, only to find the carburetor completely destroyed and in need of a rebuild.
For these reasons, marine manufacturers and small-engine makers often recommend ethanol-free fuel, especially for seasonal storage.
Octane and Engine Performance
Ethanol has a high octane rating on its own, which helps resist engine knock (the premature detonation of fuel that can damage pistons and valves). When blended into gasoline at 10%, it gives refiners a cost-effective way to reach the 87-octane regular grade without relying entirely on more expensive petroleum refining processes. For modern cars with electronic fuel injection and knock sensors, E10 performs well. Your engine’s computer adjusts the air-fuel mixture automatically, so you won’t feel a performance difference during normal driving.
Environmental Tradeoffs
E10 produces modestly lower tailpipe emissions than pure gasoline. All ethanol blends reduce carbon dioxide output compared to E0. On a lifecycle basis, accounting for growing the corn, fermenting it, and burning the final fuel, ethanol’s greenhouse gas emissions run about 46% lower than gasoline’s. That translates to roughly 53 grams of CO2 equivalent per megajoule of energy for ethanol versus 98.5 grams for gasoline. Since E10 is only 10% ethanol, the real-world reduction at the tailpipe is proportionally smaller, but it scales across billions of gallons consumed nationally each year.
Higher ethanol blends show more dramatic benefits. Bumping from E10 to E15 cuts carbon monoxide emissions by 17% and particulate matter by 18%. Nitrogen oxide emissions, which contribute to smog, drop as much as 70% in mid-level blends like E20 and E30 compared to E0.
Storage Life
E0 stores longer and more reliably than E10. Without ethanol pulling moisture into the fuel, pure gasoline in a sealed container stays usable for a year or more without treatment. E10 in a sealed, temperature-controlled environment can last six months or longer without issues, but the clock starts ticking faster in humid conditions or containers that aren’t airtight.
If you need to store E10 for more than a few months, adding a fuel stabilizer extends its usable life significantly. For seasonal equipment you won’t touch until next year, either run the engine dry before storage or fill it with ethanol-free gas treated with stabilizer.
Where to Find E0
E0 is less common than E10 and typically costs 20 to 50 cents more per gallon. Not every station carries it. Marinas often stock it, and some gas stations in rural areas or near recreational areas advertise ethanol-free fuel on a dedicated pump. Websites like pure-gas.org maintain searchable databases of stations selling E0 across the country.
For everyday driving in a modern car, E10 is perfectly fine and what your engine was designed to run. E0 makes the most practical difference when you’re fueling equipment that sits idle, running older engines without ethanol-compatible components, or storing fuel for emergency preparedness.