E85 Ethanol and Vintage Cars

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).

3 thoughts on “E85 Ethanol and Vintage Cars

  1. Interesting article. I’ve ran (E10) thru my ’01 Dakota 4.7L magnum (not exactly “vintage”, but not new either) a few times and every time I do the dummy light comes *on* within ~10 miles. So I plugged in the coded reader and it spits out codes that the #3 O2 sensor is malfunctioning. So then I go fill up with regular gasoline and the dummy light goes *out* within ~10 miles.

    I guess this could be due to residue and junk coming loose and fouling the O2 sensor, or could be that the sensor is on it’s way out anyway. But it’s interesting that it only happens when I run a (mild) E-mix and then that regular gasoline kills the dummy light in short order. And this is only an E10 blend, so I wouldn’t attempt a more aggressive ethanol mix.

  2. The biggest Problem with ethanol in older cars is with rubber bases hoses and o-rings. You may not realize it but alcohol is very damaging to petroleum based rubber and over time the alcohol will eat the fuel lines and o-rings in the fuel system causing leaks and eventually failure of the fuel system which at best, lowers performance and at worse, can cause the car to catch fire.

    electronically controlled engines can adjust for the change in octane but carburetors need to be rebuilt with proper jets to adjust for the increase in fuel consumption.

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