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Way back in 1978, the Environmental Protection Agency (EPA) issued a waiver to the Clean Air Act, allowing gasoline that was made up of up to 10% ethanol, or E10, to be sold at the fuel pump. E10 is still the gas that is most commonly sold today.
Decades later, in 2010, the EPA would begin allowing E15 gas (15% ethanol) to be used, but only in 2007 model year cars or newer. The final rule would allow E15 to be used in 2001 cars and newer, as well as modern flex-fuel engines. E15 is normally not available in the summer, but the EPA has issued waivers in the past few years to allow its sale year-round. (Here’s why ethanol is mixed into gasoline in the first place.)
It is illegal to use E15, sold as 88 octane, in older engines. It is also illegal to use it in lawnmowers, motorcycles, boats, heavy-duty vehicles like delivery trucks, and aircraft. Why? Ethanol is not kind to engines, especially older ones, and that 15% amounts to a lot of corn juice blended into your gasoline. If an engine isn’t built to deal with ethanol, it can do a lot of damage. But regardless of how old your car is, you should check to see if your manufacturer has even authorized E15 gas to be used in it. Most manufacturers have only authorized its use in cars much newer than 2001, and some don’t allow it at all.
The effects of E15 gas on the wrong engines
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So why can’t you just use E15 in any gas engine? Ethanol is a solvent, and a powerful one at that. Solvents are really bad for rubber, plastic, and aluminum, causing them to deteriorate over time. Think of all the rubber hoses and seals, as well as the many plastic and aluminum parts that are in a typical engine. If an engine isn’t designed for a significant amount of ethanol in the gasoline that runs through it, E15 can cause a lot of damage.
And then there’s the fact that ethanol attracts water because it is alcohol-based. In fact, it can even draw water from outside the tank — and bad things happen when water finds its way into your car’s gas tank. You’ve likely heard horror stories about how bad that can be for an engine. But when water is pulled into a gas tank filled with an ethanol blend, the ethanol will separate from the gasoline, with the water and ethanol settling on the bottom, while the gas rises to the top. Obviously, it’s bad news if the separated water and ethanol reach the engine. But even the separated gas is bad for the engine, because much of the octane is attached to the ethanol, meaning the separated gas will have less octane and likely cause your engine to knock. This separation typically happens in gas tanks that sit for a while.
Why you might not want to use E15 in the right engines either
So you have a car newer than 2001, or maybe you have a newer flex-fuel model. Is using E15 gas a good idea? It’s still not ideal. Ethanol is not as dense as gasoline. That means the more ethanol a gas blend has, the less efficient it is. So E15 would be less efficient than the more commonly sold E10 gas. In other words, you may not get as good gas mileage, which is kind of a big deal when gas is cresting four dollars a gallon.
And you don’t want to rely on what the EPA says about which engines can use E15, either. Many automakers haven’t approved the use of it in models older than 2013 or sometimes later. BMW doesn’t want you using it in any of its cars older than the 2020 model year. Nissan approved it for the 2018 model year in some models, but approved it in all models 2019 and newer. Mitsubishi has only approved it for some of its models to this day. Daimler, Mazda, and Volvo still haven’t approved using E15 in any of their models.
What’s more, ethanol gas isn’t even that eco-friendly. Did you know that it takes a gallon of fossil fuel to produce one gallon of ethanol? Even John Oliver knows ethanol fuel is a total fraud.
