• Ethanol is hygroscopic, which means it absorbs water more easily than gasoline. That leads to water condensation inside fuel tanks, carburetor fuel bowls and fuel lines where air spaces are present. Water content in fuel will also swell up the paper filter media inside fuel filters not specifically designed for flex fuels and can thus restrict fuel flow at the filter.
• Ethanol also erodes fiberglass tanks, rubber hoses and plastic fuel lines. It contributes to rust in fuel systems by creating condensation in the unfilled portion of gas tanks. It will also dissolve varnish and rust in steel fuel components. These dissolved ingredients sit in the bottom of gas tanks until they are removed or they will enter the fuel system if the fuel level in the tank gets too low.
• If water is present and isn’t absorbed, it sinks to the bottom of the tank, where the pickup tube sucks it into the engine. But there’s a limit to the amount of water that can be absorbed before separation occurs, so when E10 sits in a humid environment, a corrosive mixture of water and ethanol can accumulate at the bottom of the tank.
• These problems are exacerbated in lightly driven vintage cars that often have metal fuel tanks that might be poorly sealed due to degraded or missing emissions systems. This allows moist air into the tank, which gets absorbed by the ethanol in the gas, separates out as water, accumulates at the bottom of the tank, and causes running problems and rust in the tank. Ethanol also ruins rubber fuel lines, gaskets, and plastic and rubber fuel-system parts.
How to Protect Your Car
• Replace any plastic or rubber fuel lines with ethanol-resistant hose or nylon tubing.
• Install a water separator filter in the fuel line leading to the carburetor. Water collects in the filter and can be removed periodically.
• Replace any fiberglass tanks with steel or aluminum.
• Ensure that any O-rings in the fuel system are also ethanol-compatible.
• Keep your tank as full as possible to prevent air space where condensation can form.
• Use specific ethanol-compatible fuel storage additives. These are normally blue in color. Regular fuel stabilizers will not work unless they are labeled ethanol fuel-compatible.
• Shop around for a marina or service station that does not pump E10 or E85. https://www.pure-gas.org/index.jsp?stateprov=PA
• Vent your fuel system during storage for extended periods; the moisture your fuel system might absorb from the outside will be less than the moisture created in the air space inside.
• Use of isopropyl alcohol-based dry gas will help to absorb system moisture. Regular dry gas is ethanol-based and will only make the problem worse. Isopropyl-based additives actually combine with the water molecules and removing moisture through the combustion chamber.
• Use of a flex fuel-compatible fuel filter where possible will prevent degradation of the paper media in your filter by water in the fuel system.