
Most cars on the road today cannot use E51 fuel, as it's not a standard gasoline blend. If you're referring to E85 flex fuel (which is 51-83% ethanol), then the answer is specific Flex-Fuel Vehicles (FFVs). These are purpose-built to handle the corrosive nature of high-ethanol fuel. You can identify an FFV by checking your owner's manual, looking for a yellow gas cap, or finding an E85 endorsement on the inside of your fuel door. Using E85 in a non-FFV can cause significant damage to the fuel system.
The primary requirement is being a Flex-Fuel Vehicle (FFV). These models have engines and fuel systems constructed with ethanol-resistant materials. Using E85 in a standard gasoline engine can lead to corrosion of fuel lines, injectors, and seals, and may cause drivability issues due to the engine control unit (ECU) not being calibrated for the different fuel mixture.
To confirm if your car is an FFV, check these:
Historically, many American automakers produced a wide range of FFVs. Here are some examples across different brands and vehicle types:
| Car Type | Brand Examples | Common FFV Models (Circa 2010-2018) |
|---|---|---|
| Full-Size Pickup | , Chevrolet, RAM | Ford F-150, Chevrolet Silverado, RAM 1500 |
| Sedan | Chevrolet, Dodge, Ford | Chevrolet Impala, Dodge Charger, Ford Taurus |
| SUV | GMC, Chevrolet | GMC Yukon, Chevrolet Tahoe |
| Minivan | Chrysler | Chrysler Town & Country |
It's important to note that while E85 is often cheaper per gallon, its energy density is lower than gasoline. This means fuel economy (MPG) will drop by approximately 15-30%. Whether this results in savings depends on the price difference between E85 and regular gasoline in your area. Always consult your vehicle's manual for the definitive answer on fuel requirements.

Check your gas cap. If it's yellow, you're probably good for E85. If not, I wouldn't risk it. My old Chevy pickup has that yellow cap and runs fine on the stuff. It's cheaper at the pump, but you'll notice you're filling up more often. It's a trade-off. Just make sure your car is actually built for it—putting it in a regular car is asking for expensive repairs.

As a mechanic, I've seen the damage. Unless your car's manual explicitly says "E85" or "Flex-Fuel," assume it's a no-go. The ethanol can eat away at rubber hoses and plastic parts in the fuel system not designed for it. It's not worth the risk for a few cents off per gallon. If you're unsure, just stick with the recommended fuel grade. It’s the cheapest you can buy for your engine.

I switched to E85 for environmental reasons in my flex-fuel SUV. It's a renewable fuel and burns cleaner. But you have to do the math. The lower MPG means you're more fuel, so the real environmental and cost benefits depend on how it's produced and priced locally. It's a conscious choice, not just a simple gas station decision. It only makes sense if your vehicle is compatible.

The key is your vehicle's build year and model. From the early 2000s through the late 2010s, many American-made cars, trucks, and SUVs were offered as flex-fuel options. Look up your specific make, model, and year online on a reliable site like the U.S. Department of Energy's alternative fuels database. They have a comprehensive list that's more accurate than relying on memory or a gas cap that might have been replaced.


