What Is Ethanol? Is It Bad for Your Engine?

Your routine at the gas station is probably the same every time. You pull up to the pump, enter your rewards number, and flip the handle up for either regular or premium. If the pump has a little TV, you watch some influencer ramble on about a cream that cures eye wrinkles as you fill up. Either way, you are probably thinking more about that slice of pizza waiting inside than you are about anything else.

Just as gas prices fluctuate, so too will vehicle prices. The MSRP of new vehicles today averages at or near $50,000, an all-time high. Whether you are currently shopping, have recently purchased something, or are simply holding on to what you have, preventive maintenance is increasingly important given the costs associated with vehicle ownership today.

The gas we put in our daily driver is sometimes an afterthought, but in the interest of keeping your vehicle in tip-top shape, it helps to understand what the labels on the pump mean. Here is a closer look at where ethanol comes from, including how it affects your engine, what is meant by “FFV,” and when you should look for ethanol-free gas.

To gain a more complete picture of ethanol, it helps to start with a term that slowly disappeared from everyday use.

Gasohol is a finished fuel blend in which ethanol, an alcohol produced by fermenting plant material such as corn, is combined with conventional gasoline. The ethanol used in the mixture is anhydrous, meaning virtually all water has been removed beforehand, as ethanol's natural affinity for moisture would otherwise cause it to separate from the gasoline.

The term gasohol was widely used throughout the 1970s and 1980s, but has since given way to the E-number system of today. What was once called gasohol is now simply known as E10.

Ethanol is a renewable, alcohol-based fuel made from plant material, primarily corn in the United States. When blended with conventional gasoline, ethanol acts as an octane booster while also reducing emissions. Stickers or insignias on the pump that say “E10” or “E15” refer to the percentage of ethanol in the gasoline.

Interest in blending gasoline with ethanol took hold in the late 1970s. In October 1973, Arab members of OPEC imposed an embargo on the United States in response to American support for Israel during the Yom Kippur War. The embargo choked off supply almost overnight, sending ripples through the U.S. economy that were felt on both Wall Street and Main Street.

In New York City, the stock market plummeted, erasing nearly $300 billion in value over a matter of weeks and triggering a prolonged period of stagflation. In almost every neighborhood in America, lines for gas stretched for blocks as oil prices skyrocketed. Rationing rules meant citizens could buy gas only on odd- or even-numbered days of the month, depending on whether their license plate ended in an odd or even number. The Nixon Administration would soon set a national speed limit of 55 mph to conserve fuel.

In the end, the embargo exposed a critical vulnerability in U.S. energy policy and pushed the country toward domestic alternatives, ethanol among them.

Around this same timeframe, the U.S. also needed a replacement for lead, which had been used as an octane enhancer since the 1920s. By the 1970s, research was mounting that linked lead emissions from vehicle exhaust to serious health consequences, particularly in children, including developmental delays and neurological damage. When the EPA began issuing reduction standards in 1973, the process of phasing lead out of gasoline was underway.

Ethanol would soon emerge as a viable, domestically produced alternative with octane-boosting properties, minus the health risks associated with lead. The 1978 Energy Tax Act gave ethanol blending its first federal backing, followed by the 1990 Clean Air Act Amendments, which required the use of oxygenated gasoline in cities with the worst air pollution (Ethanol became one of the ways refiners met that standard).

By 1996, the mandates established in the 1990 Clean Air Act Amendments led to the complete phase-out of leaded gasoline for on-road vehicles. Today, more than 98% of the gasoline sold in the United States contains ethanol. In other words, ethanol-blended fuel is simply "regular gas."

Ethanol serves three main purposes when blended into gasoline: it boosts octane, reduces emissions, and lowers fuel production costs.

As noted a moment ago, the regular unleaded we see at the gas station is E10, meaning it already contains 10% ethanol. The ethanol content is part of what brings the fuel up to its 87 octane rating. Pure ethanol carries an octane rating of around 113, and when blended into gasoline, that naturally higher octane raises the overall fuel grade.

Meanwhile, ethanol adds oxygen to the fuel mixture, promoting a more complete burn in the combustion chamber. As a result, the combustion chamber produces less carbon monoxide and fewer unburned hydrocarbons, delivering on the changes the 1990 Clean Air Act Amendments sought when mandating oxygenated gasoline in the country's most polluted cities.

Beyond its performance and environmental benefits, ethanol is often cheaper to produce than petroleum, evidenced in the generally lower per-gallon prices we have seen over the years.

Is Ethanol Bad for Your Car or Truck?

For most vehicles on the road today, no. At the blend levels found at any standard pump, ethanol will not harm a properly maintained car, truck, or SUV. Since the 1990s, automakers have built vehicles with ethanol-compatible fuel system components, including lines and seals.

In other words, there is no need to think twice at the gas station. You can fill your pickup and any other vehicle you own with regular unleaded, which will already have an ethanol blend.

For turbocharged truck engines like Ford's 3.5-liter and 2.7-liter EcoBoost, the ethanol blended into regular unleaded gasoline works in the driver's favor. Ford recommends 91 octane or higher for best performance in those engines, but both are designed to run on regular unleaded (i.e., 87) regardless. EcoBoost F-150 owners still receive the octane and emissions benefits of ethanol by filling up with regular unleaded, and at a lower cost than reaching for the premium handle.

E15 takes that a step further, bumping the ethanol content to 15% for an octane rating of 88. It is approved for vehicles built in 2001 and newer, and for a truck that can handle it, the extra octane is there if you want it.

Ethanol becomes a concern in older trucks or in any vehicle that sits unused for months at a time. Since ethanol absorbs moisture from the air, a phenomenon known as phase separation can occur, in which the water-ethanol mixture separates from the gasoline and settles at the bottom of the tank. Rough starts, hesitation, and fuel system corrosion are primary warning signs.

If you have a vehicle that falls into this category, you will want to look for ethanol-free gas.

Ethanol-free gasoline is 100% petroleum with no alcohol added. You will most often find it sold as Rec 90, short for recreational 90-octane. The “recreational” label comes from the fuel’s primary market, which includes owners of boats, watercraft, and other recreational vehicles with small engines sensitive to ethanol's moisture-absorbing properties.

Is Ethanol-Free Gas Really Better?   

Rec 90 will run fine in any late-model car, truck, or SUV, but benefits may be marginal, if any.

Since pure gasoline has a higher energy density than an ethanol-blended fuel, you may see a slight improvement in gas mileage, but likely not enough to justify the added cost. On average, Rec 90 typically costs about a dollar more per gallon than E10.

Instead of using Rec 90 for your current vehicle, consider it for a classic car, prized show truck, or weekend toy. Rec 90 can be advantageous for something that sits for an extended period, such as during a long winter. As mentioned above, ethanol-blended fuel absorbs moisture from the air, which can cause phase separation, gummed injectors, and hard starts. Ethanol-free fuel does not have the same moisture risk and can remain stable for up to a year or longer when stored with a quality fuel stabilizer.

Where to Find Ethanol-Free Gas

You can usually find Rec 90 at stations near marinas and airfields, as well as in rural areas that deal with farm and agricultural equipment. The website Pure-gas.org maintains a crowdsourced, regularly updated map of ethanol-free stations across the United States and Canada.

At the far end of the spectrum is E85, a high-ethanol blend that contains anywhere from 51% to 83% ethanol, with the remainder being gasoline. The blend varies by region and season, with higher ethanol content in warmer months and lower content in winter to aid with cold starts. E85 is only for Flex-Fuel Vehicles, commonly identified by a yellow fuel cap or an FFV badge on the exterior. Many full-size trucks from Ford, GM, and RAM have been offered as FFVs over the years.

For FFV owners, E85 offers a performance upside. Because of its higher octane rating, E85 gives the engine more to work with, resulting in more horsepower and torque from the same stock components.

For example, GM officially published two separate power ratings for the 5.3-liter EcoTec3 V8 found in 2014 through 2017 flex-fuel versions of the Chevy Silverado 1500 and GMC Sierra 1500. On regular unleaded, the engine is rated at 355 horsepower and 383 lb-ft. of torque. On E85, those numbers climb to 380 horsepower and 416 lb-ft. of torque.

The same 5.3-liter V8 also powered flex-fuel versions of the Chevy Tahoe and GMC Yukon through the 2016 model year, where the same E85 performance advantage also applies.

The trade-off with E85 is fuel economy. For example, a 2017 Chevy Silverado on E85 returns an EPA-estimated 11 in the city, 16 on the highway, and 13 combined. On regular unleaded, those figures improve to 16 in the city and 22 on the highway with a combined MPG of 18.  

Ethanol-blended gasoline will not hurt a well-maintained vehicle, especially a late-model car, truck, or SUV. On the contrary, most vehicle owners benefit from the widespread availability of ethanol as it provides a modest octane boost, cleaner emissions, and a small price-per-gallon cushion at the pump. However, when in doubt, always refer to your owner's manual or any labels on your fuel cap.

If your prized show truck or classic Detroit muscle car sits over the winter until it is summertime again, switch to Rec 90 and add a fuel stabilizer from a trusted brand like Lucas Oil to protect the fuel system.

Otherwise, try not to overthink it. Simply match the fuel to how you use your vehicle, and it will take care of you.

Q: What Is E10 Gas?

E10 is gasoline blended with 10% ethanol. It is the most common fuel sold in the United States and is compatible with all gasoline-powered vehicles on the road today.

Q: What Is E15 Gas?

E15 is gasoline blended with 15% ethanol, also labeled and marketed as Unleaded 88. It is EPA-approved for vehicles built in 2001 and newer and is generally priced lower than standard E10 at stations that carry it.

Q: Does Premium Gas Have Ethanol?

At most pumps, premium gasoline contains the same E10 blend as regular unleaded. The higher octane rating of premium reflects how the fuel is refined, not its ethanol content. Those who need ethanol-free fuel should look for Rec 90 rather than assuming that premium means no ethanol.