What Is Flex Fuel and How Does It Affect My Vehicle?

If you have a flex fuel vehicle, or if you’re looking to purchase one, you’ll be pleased to know that the technology isn’t exactly complicated to use or expensive to own. Here’s the rundown on how flex fuel vehicles work and what responsibility you have as an owner of one.

What Does Flex Fuel Mean?

“Flex Fuel” means that your vehicle can run on two different mixtures of fuel, and it can switch between these mixtures automatically. The two different mixtures are:

  1. Standard pump gasoline, which is a blend of 10-15% ethanol and 90% gasoline
  2. E85, which is a blend of 15% gasoline and 85% ethanol

E85 isn't a common fuel option - you won't find it at every gas station - but it's available in most large metro areas and particularly common in the midwestern USA (anywhere corn is grown, as corn is the primary source of ethanol).

If you have a flex fuel vehicle, it means that your engine can function on standard gasoline OR E85 without suffering any sort of damage. Unlike standard engines, E85 engines have a handful of upgrades:

  • Flex fuel vehicles have fuel pumps, fuel lines, fuel injectors, and a fuel tank that are resistant to corrosion/deterioration that can be caused by ethanol
  • The cylinders, pistons, valves, and other internal components of a flex fuel engine are specially coated to protect them from various corrosive chemicals that can be created during the combustion of E85
  • Flex fuel engines also have larger fuel pumps and injectors because of the lower energy density of E85 compared to standard pump gas (more on that later)

Finally, a flex fuel engine is able to detect ethanol in the fuel system and adjust combustion accordingly. This means that you can mix E85 with regular gas however you like. Fill the tank with E85 today, then put regular gas in tomorrow and no problem. The engine will adjust.

NOTE: E85 is extremely dangerous to non flex-fuel vehicles. At the very least, E85 will quickly damage the fuel system in a non flex-fuel vehicle, and internal engine damage is a possibility. Never put E85 in your vehicle unless you *know* it's flex fuel compatible.

The Pros and Cons of Owning a Flex Fuel Vehicle

Starting on the "pro" side of things:

  • Consumers don’t generally pay more to buy a flex fuel compatible vehicle. GM - and other automakers - produce these flex fuel vehicles for the same cost as "regular" vehicles.
  • In some areas, E85 is substantially less costly than regular pump gasoline.
  • An engine that can run on E85 is a little more resistant to damage from contaminated fuel (depending on the contaminant)
  • If you choose to run your flex fuel vehicle on regular gasoline, there's no extra maintenance or service needed
  • Using E85 reduces C02 emissions by an average of 34% compared to gasoline, since 85% of a gallon of E85 is sourced from plants rather than drilled out of the ground

Driving on E85 is good for the environment and can be a way to save some money. What's more, if you own a flex fuel vehicle but you decide not to buy E85, you don't have to give the system a second thought. There's no downside whatsoever to owning a flex fuel vehicle that only runs on pump gas. However, if you have a flex fuel vehicle and you start driving on E85, there are some "cons" you need to know about:

  • E85 has about 15% less energy per gallon than regular pump gas. This means that your gas mileage drops 15% whenever you burn E85 compared to regular pump gas.
  • If you run your vehicle on E85 for more than a few hundred miles, you need to adjust your oil change schedule. Most manufacturers recommend that you change the engine oil on the 'severe duty' schedule, which basically means you're changing your oil every 3,000 miles instead of every 5,000 or 7,500.
  • E85 can sometimes become contaminated during transportation or storage, meaning that you're a little more likely to buy a bad "batch" of E85 than you are regular pump gas. If you get a bad tank of E85, you'll probably notice your engine runs poorly.
  • E85 prices change considerably from one station to the next. If you're driving across country and determined to drive only on E85, you might be shocked at what you're asked to pay at some stations

Still, as you can see, the "cons" aren't to serious. You won't get the same gas mileage, you'll need to change your oil a little more frequently, and that's about it.

How Do I Know If I Have a Flex Fuel Vehicle, and Where Can I Get E85?

If you’re not sure if you have a flex fuel vehicle, the most obvious sign (besides the badging) is if your vehicle has a yellow gas tank cap. You can also check your vehicle’s owner’s manual for an explanation about the engine and types of fuel it accepts.

If you're looking for a place to buy E85, there are plenty of E85 maps out there, and your local GM dealer probably knows exactly where to find E85 in your area.

Last but not least, many drivers own a flex fuel vehicle and don't know it. According to the Nebraska Corn Board, 60% of the state’s residents had no idea they were driving a flex fuel vehicle (FFV). That stands as a testament to how easy flex fuel equipped vehicles are to own and maintain.