Choosing the right fuel isn’t always as straightforward as pulling up to the cheapest pump. With options like E85, diesel, and regular unleaded, using the wrong type of fuel—or simply an inefficient one for your vehicle—can hurt your engine and your wallet.
This guide breaks down the key differences between common fuel types so you can make the smartest choice for performance, efficiency, and cost.
- Regular Unleaded (87 Octane): The Standard Choice
Regular unleaded gasoline is the most common and affordable fuel type used in the majority of passenger vehicles. It’s designed for engines with standard compression ratios and offers reliable performance without the premium price.
When to use it:
- Your car manufacturer recommends 87 octane
- You drive a typical sedan, SUV, or light-duty vehicle
- You want the most budget-friendly option that still meets performance needs
Using premium fuel in a car that doesn’t require it will not improve performance or mileage—it just costs more. Learn more at fueleconomy.gov.
- Premium Gasoline (91–93 Octane): Use Only If Required
Some high-performance engines are designed to run on higher-octane fuel to prevent knocking and improve efficiency. However, if your owner’s manual only recommends premium rather than requires it, regular fuel is usually sufficient for everyday driving.
When to use it:
- Your car’s engine requires it to avoid knock or pre-ignition
- You drive a turbocharged or high-compression engine
- It’s specifically listed in your owner’s manual
- Diesel: For Torque and Towing Power
Diesel fuel is more energy-dense than gasoline, which means diesel engines typically get better fuel economy and are ideal for heavy-duty trucks, long-haul vehicles, and vehicles designed for towing. However, using diesel in a gasoline engine—or vice versa—can seriously damage your engine.
When to use it:
- Your vehicle is specifically designed for diesel fuel
- You need long-distance fuel efficiency and torque (for example, in pickups or large vans)
- You want extended engine life with proper maintenance
Check diesel station availability on apps like GasBuddy if you drive outside urban areas frequently.
- E85 (Flex Fuel): High Ethanol Blend with Lower Cost
E85 is a fuel blend containing up to 85% ethanol and 15% gasoline. It typically costs less than regular gas but delivers fewer miles per gallon due to ethanol’s lower energy content.
Only flex-fuel vehicles (FFVs) can use E85. You can confirm this by looking for a yellow gas cap or a label inside your fuel door. The U.S. Department of Energy offers a vehicle search tool to confirm FFV compatibility.
Pros of E85:
- Lower pump price
- Supports renewable fuel initiatives
- Available at select stations in the Midwest and South
Cons of E85:
- Lower fuel economy (up to 25% less than gasoline)
- Limited availability outside certain regions
- What Happens If You Use the Wrong Fuel?
- Diesel in a gas car: Can lead to engine failure, fuel system damage, and costly repairs.
- Gas in a diesel car: May cause severe knocking and stalling.
- E85 in a non-flex fuel vehicle: Risk of engine misfires and long-term damage.
Always follow your owner’s manual to avoid misfuelling and ensure optimal performance.
Bonus Tip: Match the Right Fuel with Smart Spending
No matter which fuel type your vehicle requires, you can still cut costs by using price comparison apps like Waze or GasBuddy. Drivers who use cashback platforms like Fluz can earn instant cashback when they buy fuel gift cards from participating stations like BP.
Final Thoughts
Fuel type affects everything from mileage and performance to maintenance and cost. Stick with what your vehicle was built for and look for fuel-specific savings tools to optimize your refueling routine. It’s not just about filling up—it’s about fueling smarter.
