What is E85? A Complete Guide to Flex Fuel

If you’ve ever noticed yellow gas pumps at your local station or heard someone mention “flex fuel,” you might be wondering what E85 is all about. E85 is an ethanol-heavy fuel blend consisting of up to 85% ethanol and 15% gasoline, making it the highest ethanol fuel blend available at retail pumps. Let’s dive into everything you need to know about this alternative fuel.

Understanding E85 Composition

The “85” in E85 doesn’t always mean exactly 85% ethanol. In the United States, federal regulations specify that E85 can contain anywhere from 51% to 83% ethanol. This variation isn’t random—it’s intentional and practical.

Why Does the Ethanol Content Vary?

The ethanol percentage in E85 is adjusted seasonally and geographically to ensure proper vehicle starting and performance in different temperature conditions. During cold weather, ethanol’s lower heating value makes it difficult to start engines, which is why winter blends contain less ethanol and more gasoline. Summer blends typically have higher ethanol content, while winter formulations may drop to as low as 51% ethanol to ensure reliable cold-weather starting.

How E85 is Made

E85 ethanol generally comes from domestic sources, with corn being the primary feedstock in the United States. Ethanol is a renewable, domestically produced alcohol fuel made from plant materials such as corn, sugar cane, or grasses. This domestic production is one of the key reasons E85 has gained support as an alternative to imported petroleum.

Who Can Use E85?

Here’s the most important thing to know: E85 can only be used in flex fuel vehicles (FFVs).

Flex fuel vehicles are specifically designed to run on E85, regular gasoline, or any ethanol blend ranging from E0 to E85. These vehicles have specially designed fuel systems and engine components that can handle ethanol’s unique properties.

How to Tell If Your Vehicle is Flex Fuel Compatible

Most flex fuel vehicles feature obvious exterior badging stating “Flex-Fuel,” “FFV,” or “E85.” Many also have a yellow fuel cap to match the yellow sheathes on E85 pumps. If your vehicle has a capless fuel filler, look for a yellow ring around the opening. When in doubt, check your owner’s manual or the manufacturer’s website.

E85 vs. Regular Gasoline: Key Differences

Energy Content and Fuel Economy

Due to ethanol’s lower energy content, vehicles operating on E85 typically get roughly 15% to 27% fewer miles per gallon compared to regular gasoline, depending on the ethanol content. Ethanol contains about one-third less energy than gasoline, which explains this decrease in fuel economy.

In real-world testing, a 2007 Chevrolet Tahoe FFV achieved 26.5% worse fuel economy on E85 compared to gasoline. However, the actual difference varies by vehicle, driving conditions, and ethanol content.

Octane Rating and Performance

E85 has a higher octane rating than regular gasoline’s typical 87 rating or premium gasoline’s 91-93 rating. Some flex fuel vehicles actually perform better—producing more torque and horsepower—when running on E85 than on regular gasoline.

The higher octane allows for more aggressive engine timing, which can result in increased power output, especially in turbocharged or performance-tuned vehicles.

Cost Considerations

E85 typically costs around 60 cents less per gallon than regular gasoline, making it appear cheaper at the pump. However, because of the reduced fuel economy, the cost per mile may actually be similar to or slightly higher than regular gasoline, depending on the price difference in your area.

Environmental Benefits

E85 can provide important reductions in greenhouse gas emissions compared to petroleum-derived gasoline or lower volume ethanol blends. E85 is less volatile than gasoline, resulting in fewer evaporative emissions, and using E85 reduces carbon monoxide emissions and provides significant reductions in emissions of many harmful toxics, including benzene, a known human carcinogen.

Additionally, because ethanol is made from renewable plant sources rather than fossil fuels, it helps reduce dependence on imported oil and supports domestic agriculture.

E85 Availability

There are more than 3,900 E85 refueling stations across 42 states, though availability varies significantly by region. E85 is most commonly found in Midwest states where corn production is highest. If you’re looking for E85 stations near you, websites like E85GasFinder.com can help you locate the nearest pumps.

Is E85 Right for You?

E85 can be a good choice if you:

• Own a flex fuel vehicle
• Live in an area with readily available E85 stations
• Find E85 priced significantly lower than regular gasoline (typically $1 or more per gallon cheaper)
• Want to reduce your environmental impact and support domestic fuel production
• Have a performance vehicle that can benefit from E85’s higher octane rating

However, E85 may not be practical if:

• Your vehicle isn’t designed for flex fuel
• E85 stations are scarce in your area
• The price difference doesn’t offset the reduced fuel economy
• You frequently drive in extremely cold weather

The Bottom Line

E85 is a topic of increasing relevance in discussions of gasoline’s environmental impact and shifting energy reliance from foreign oil to renewable energy sources. While it’s not the perfect solution for everyone, flex fuel and E85 offer drivers with compatible vehicles an alternative that supports domestic agriculture, reduces certain emissions, and can provide cost savings depending on local fuel prices.

Before switching to E85, always verify your vehicle’s compatibility and calculate whether the fuel economy trade-off makes financial sense based on the price difference in your area. With the right vehicle and circumstances, E85 can be an excellent choice for your wallet and the environment.