Fueling Up: What Car Owners Need to Know

As many of us have noticed, gas prices are on the rise, but that’s not the only thing increasing in our fuel. Typically, gasoline is allowed up to a 10% ethanol blend, but on May 1st the EPA released an emergency waiver allowing gas to contain up to 15% ethanol.

Modern cars barely notice the difference because they were built with ethanol-compatible fuel systems and computers that constantly adjust fuel delivery. Many cars can even run an 85% ethanol blend, also commonly referred to as e85. These vehicles are known as flex-fuel vehicles. In cars built after 2001, the only difference you may notice is a slight drop in fuel efficiency. Ethanol contains less energy per gallon than regular gasoline, roughly 30–35% less. Because of this, your engine has to burn more fuel to create the same amount of power. Unfortunately, older classic cars are a different story.

Classic carbureted cars tend to hate ethanol for a few reasons. The biggest problem is that ethanol attracts moisture, and moisture inside an old steel fuel tank or carburetor is never a good thing. If a vintage car sits for a few months, corrosion, sticky varnish deposits, and clogged jets can start to develop. Older rubber hoses, accelerator pump diaphragms, and seals also weren’t designed for alcohol-blended fuel, so they can dry out, crack, or turn gummy over time. On top of that, since ethanol carries significantly less energy than straight gasoline, it can create lean conditions in carbureted engines, causing them to run hotter or less efficiently.

So, what can you do? If you drive a modern vehicle, just keep using the fuel your manufacturer recommends. If you’re driving a car older than 2001, or one with a carburetor, try to find ethanol-free fuel. Many gas stations still carry it, though it usually sells at a premium price. If you plan on storing your car for any period of time, try to get as much fuel out of the tank as possible and use a fuel stabilizer before parking it. That can help prevent buildup, corrosion, and cracking in older rubber fuel lines.