You can put either regular gasoline or E85 ethanol blend in a flex-fuel vehicle (FFV). The key is to use fuels within the E10 to E85 range, meaning any blend containing between 10% and 85% ethanol. Your car's engine control unit (ECU) is designed to automatically adjust its settings to accommodate whatever blend is in the tank. This flexibility is the core feature of an FFV.
Identifying Your Flex-Fuel Car
Not every car can handle E85. Look for these clear indicators: a yellow gas cap, a badge on the trunk or sides saying "FlexFuel," "E85," or "FFV," and a mention in your owner's manual. The vehicle identification number (VIN) can also be decoded online to confirm it's an FFV.
Gasoline (E10) vs. E85: Key Differences
The choice between standard gasoline and E85 involves a trade-off between cost, performance, and fuel economy.
| Fuel Type | Ethanol Content | Typical Cost per Gallon | Fuel Economy (MPG) | Horsepower/Torque | Key Consideration |
|---|
| Unleaded Gasoline (E10) | Up to 10% | Higher | Better (Baseline) | Standard | Widely available; consistent performance. |
| E85 (Flex-Fuel) | 51-83% | Lower | Reduced by 15-30% | Potential slight increase | Lower energy content; check local availability. |
E85 has a higher octane rating (typically 100-105) than regular gasoline (87-93), which can allow for more aggressive engine tuning and a slight power boost in some high-performance applications. However, ethanol contains less energy than gasoline, which is why you'll get fewer miles per gallon. The price of E85 needs to be significantly lower than gasoline for it to be cost-effective on a per-mile basis.
Practical Advice and Precautions
It's perfectly safe to switch between gasoline and E85 as needed; you don't need to run the tank dry. Just fill up with whatever is most convenient or economical. However, never put E85 in a vehicle not designed for it, as it can cause severe damage to the fuel system and engine. If you're unsure whether your car is an FFV, stick with unleaded gasoline (E10) to be safe.
