Does ethanol harm vintage vehicles?

February 1, 2009 | By Richard Prince


What are your thoughts on using today’s fuels with 10% ethanol in older engines? I’m currently working on a 1956 Dodge Pickup with the original flathead 6 engine and a 1966 Mustang with a 1978 302 cid engine and I’m wondering how the 10% ethanol will affect the fuel systems in these vehicles.

People complain about today’s oil and about how you need a fuel system designed specifically for flex fuel before you can use it but what about ethanol in today’s gas? Will it harm any parts in the fuel systems?

For example, will it harm the gas lines, carburetor, gas tank, etc? Any advice or suggestions would be appreciated.


Ethanol, a grain alcohol derived from plant sources such as corn and sugarcane, is blended into gasoline nearly everywhere in America. Newer vehicles are engineered to run on ethanol without any difficulties but some older vehicles may experience problems when run on fuel containing it.

Ethanol is an electrolyte, which means that it will dissociate into ions and conduct electricity. In practical terms, this means it generally will promote corrosion when certain dissimilar metals come in contact with one another.

Also, ethanol is hygroscopic, which is a fancy way to say that it readily absorbs water. Water in ethanol will normally cause or accelerate the corrosion of metal components it comes in contact with, including the fuel tank and lines, fuel pump, carburetor floats, and so on.

Moreover, ethanol is incompatible with some types of rubber. Rubber parts in the fuel systems of your vintage vehicles, including hoses, seals and gaskets may harden, distort or even dissolve, leading to component failure, damage to other areas of the fuel system and engine, and fuel leaks.

Whether or not your Dodge Pickup or Mustang will be affected by any of these problems depends on a number of different variables, including whether and how susceptible their fuel system parts are and exactly how much ethanol is in the fuel blend you use.

Most people do not see any apparent problems from using the now-common 10% ethanol/gasoline blend.

Bear in mind, however, that deterioration of seals and other parts may be occurring at a slow enough rate that it’s very difficult to immediately detect.

The safest course of action, obviously, is to avoid ethanol blended fuels altogether but in an increasing number of areas this is not possible.

The second safest course of action is to replace as many of the potentially vulnerable components in your car as is feasible with ethanol-safe substitutes.

If you don’t want to go to the trouble and expense of doing this and the ethanol blend doesn’t seem to be hurting anything, at least not immediately, there are a few things you can do to diminish the likelihood of problems in the future. Drain all the gas out of the tank and the rest of the fuel system if you’re going to store the truck or car for a lengthy period of time. If you’re not going to put the vehicles into long-term storage then do your best to keep their tanks filled all the way up. If the tank is full then moisture-laden air is displaced, reducing the amount of water that gets absorbed into the fuel.