A question was recently asked if someone should, or could, use E85 fuel in a 1972 gasoline collector’s car.
The short answer is, no. E85 ethanol is a very poor idea to use in vintage cars.
A mixture of 85% ethanol and 15% gas, E85 ethanol, should not be consumed by any vehicle unless it is designated at the manufacturer as a “flex-fuel” vehicle. If you use E85 in a strictly gasoline car, not just a vintage collectible car, it may damage it beyond repair. E85 ethanol in a vehicle that is not made for e85 can cause major corrosion through out the entire fuel system, crack seals and hoses and it can remove lubrication off the engine’s cylinders. Also, both the E85 ethanol and widely available E10 ethanol will move old sludge buildup, varnish and other dirts from the fuel tank. As soon as these are within the fuel, it will cause fuel line and filter clogging as well as prohibit fuel injectors and carburetor jets from spraying correctly.
Despite its higher octane number, e85 ethanol has less energy then gasoline per gallon. In the industry, it has become a well-known fact that E85 in a “flex-fuel” vehicle capable of using gasoline. E85, will provide less miles per gallon compared to gasoline (Ethanol industry generally estimates it to be about a 30% drop).