The vast majority of gasoline you'll find at the pump has a small amount of ethanol added to it. Adding ethanol to gasoline helps reduce engine emissions, and it doesn't typically impact the performance of modern cars. For classic car owners, however, it's a good idea to use ethanol-free gasoline whenever you can. Classic cars were manufactured before ethanol was regularly added to gasoline, so they weren't designed to combat some of the issues that arise when gasoline is blended with ethanol. Below, you'll learn about some problems that can be caused when using ethanol-added gas in a classic car.
Rust in Your Fuel Tank
One of the biggest issues with using ethanol in a classic car is that it can cause your car's metal fuel tank to rust. Ethanol is hygroscopic, which means that it will absorb moisture from the air, and this includes the air that's at the very top of your car's fuel tank. Water will collect in the fuel tank as the ethanol in the gasoline draws moisture from the air, and this can cause your metal fuel tank to rust from the inside out.
Ethanol drawing moisture from the air is a major problem for classic car owners in particular because classic cars typically aren't driven very often. Since you're not using the gasoline in your tank and refilling it periodically, water builds up at the bottom of the tank and makes it more likely to rust. Modern cars use plastic liners in their fuel tanks which prevent them from rusting, allowing them to use gasoline that contains ethanol without issue. For classic cars, however, it's best to use ethanol-free gas to reduce the risk of your fuel tank rusting.
Corroded Fuel Lines and Gaskets
Classic cars weren't designed to use gasoline that has ethanol in it, and gasoline containing ethanol is more acidic than ethanol-free gasoline. Ethanol can corrode the rubber components of your car like its fuel lines, seals, and gaskets. This is another issue that's made worse when you don't drive your classic car often, as keeping your car parked allows the ethanol to sit in your fuel lines and slowly corrode them.
Modern cars have fuel lines and seals made from semi-synthetic rubber that does a better job of withstanding ethanol's acidity since modern cars were designed to account for the problems posed by ethanol in gasoline. Classic cars, on the other hand, should use ethanol-free gasoline to preserve their rubber components.
Poor Performance
Finally, gasoline that contains ethanol can reduce your car's performance. Gas mileage is the most affected since ethanol contains less energy than gasoline — blending gasoline and ethanol will reduce the number of miles you'll get from a full tank of gas. Engine performance can be affected as well since ethanol doesn't combust as easily as gasoline. Using gasoline with added ethanol in a classic car can result in the engine misfiring when it struggles to combust the mixture in the engine cylinder. The engine in a classic car simply was never designed to run on a mix of gasoline and ethanol.
If you have a classic car and want to keep it in the best condition possible, it's a good idea to fill it up at an ethanol-free gasoline station. While gas stations offering ethanol-free gasoline tend to be uncommon, using ethanol-free fuel in your classic car will help prevent the fuel tank from rusting and your rubber components from disintegrating.