What is Flex Fuel? A Complete Guide
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What is Flex Fuel? A Complete Guide

By Jason Collins | September 21, 2021

Flex-fuel is short for flexible fuel, an alternative fuel made of a mixture of either gasoline and methanol or gasoline and ethanol.

What does flex-fuel mean for car shoppers? If you are looking for a more environmentally-friendly vehicle as your next car purchase, then flex-fuel is a term worth keeping an eye out for.

Whether you plan on purchasing a new vehicle that takes flex-fuel or simply want to better understand what flex-fuel means, this article is worth the read.

What is Flex-Fuel?

Technically speaking, flexible fuel is a technology that allows an engine to burn any combination of alcohol in gasoline ranging between 15% to 85% anhydrous ethanol.

In basic terms, flexible fuel is an alternative type of fuel to regular gas. The gasoline-ethanol blend contains between 51% and 83% ethanol, with the exact ratio dependant on the geographic location and season.

Other than gasoline, ethanol and methanol are the prime ingredients in flex-fuel. Pure ethanol is essentially grain alcohol, and it is primarily made from corn in the United States. Methanol is also known as wood alcohol and methyl alcohol. It is produced through the destructive distillation of wood and is generally less popular than ethanol as a fuel additive. Touted as being cleaner than gasoline, ethanol burns cleaner and with less carbon monoxide than gasoline. It also burns more fully than gasoline, which means overall fewer emissions.

By law, and according to the ASTM (the American Society for Testing and Materials), fuel pumps marked "E85" must only dispense fuel mixtures containing between 51 and 83 percent ethanol in gasoline. The pump octane number of E85 is usually 110, instead of gasoline's 84 to 93 octane ratings, which can withstand more compression before engine knocking or auto-igniting.

Where Does Flex-Fuel Come From?

Ethanol is a domestic energy source that helps us reduce the need for imported or foreign oil. America is the world's largest producer of ethanol, producing around 16 gallons annually. Brazil and the U.S. account for 85% of the world's ethanol production. Most of Brazil's ethanol comes from sugar cane, while 98% of the State's production comes from corn.

The Midwest produces up to 72% of the total ethanol in the U.S., which includes the following states:

  • Iowa
  • Nebraska
  • Illinois
  • Minnesota
  • Indiana
  • South Dakota

Flexible Fuel Vehicles

Flexible fuel vehicles (FFVs) have an internal combustion engine designed to operate on more than one fuel type. Other than a few modifications to the car's engine and fuel system, and a different powertrain calibration, flex-fuel vehicles are almost identical to gasoline-only cars.

The Ford F-150 is an excellent example of a flex-fuel car since it is available with flex-fuel powertrains, including the 3.3-liter and 5.0-liter engines. To accommodate the E85 fuel mixture, flex-fuel F-150s have unique fuel lines. Their fuel system is lined with a nickel coating on the inside diameter of the fuel lines. The Ford F-150 also has a higher volume fuel pump and fuel delivery modules with aluminum rotors.

How to Identify a Flex-fuel Vehicle

To determine whether you have a flex-fuel car, look for these three things:

  • Badges on the exterior of the vehicle--sometimes you may find one on the inside.
  • A label on the inside of the fuel door.
  • A yellow ring around the fuel filler or a yellow gas cap.

You could also consult your owner's manual.

Current Flex-Fuel Vehicles

Below are a few examples of new vehicles with an FFV option:

  • Ford Transit Connect Transit Wagon LWB
  • Ford Taurus 3.0L
  • Chevrolet Impala
  • Ford F-150
  • Ford Escape
  • Chrysler 300
  • Mercedes-Benz CLA240 4Matic
  • Toyota Corolla VVT - iFlex
  • Honda Fit

The Advantages of Flex-Fuel

Below are some of the benefits of flexible fuel and why you may want to consider the switch from regular gas to flex-fuel.

Better for the Environment

According to Car Bibles, more Americans are concerned about their car's fuel consumption on the environment. Ethanol burns faster than gasoline, which means flex-fuel vehicles are more environmentally friendly because they pump fewer toxic fumes and fewer greenhouse gases into the air.

Ethanol is a sustainably produced fuel product made from ingredients such as corn and cane sugar. This makes flex-fuel a better alternative to foreign oil.

Burning Facility

Probably one of the biggest benefits of a flex-fuel vehicle is that it can burn whatever proportion of fuel mixture is available in its combustion chamber. FFVs are equipped with specialized electronic sensors that gauge the fuel mixture blend, while the microprocessors adjust the fuel injection and the timing.

Improved Performance

Some people may argue that using an alternative fuel mixture can negatively affect your vehicle's overall performance; however, it can actually have the opposite effect. FFVs don't experience a loss in performance when fueled with E85 fuel; contrary to the argument, some have reported an increase in horsepower and torque.

Tax Credits

Car owners who own flex-fuel cars receive tax credits. This benefit means they can significantly reduce or even eliminate their tax obligations.

The Disadvantages of Flex-Fuel

While weighing up the benefits of flex-fuel, it is important to explore the disadvantages too. Below are some of the cons to using flexible fuel.

Sole Crop Use

Even though flex-fuel is under sustainable production, the production comes with a downside; the crops become a dedicated resource for producing flex-fuel only. This means that the price of animal feed could potentially increase. It is also important to remember that corn is susceptible to adverse weather conditions, such as drought and flooding, and disease. This could be problematic for the price of corn during poor harvests.

Possible Engine Damage

Ethanol absorbs dirt quickly, which can cause corrosion and damage your engine without regular maintenance.

Gas Mileage

Flex-fuel is indeed likely to decrease the fuel economy of a vehicle using it. Ethanol raises the octane level of a vehicle slightly, which would, in theory, improve gas mileage. However, ethanol has a lower energy content compared to regular gasoline, which means that about 1.5 times more ethanol is needed to have the same energy as gas. In the end, some research shows that this equals similar gas mileage, while other research has ethanol coming up short.

For the consumer, one thing to consider is that ethanol typically costs less than gasoline, so the expense of reduced gas mileage could potentially be mitigated that way. It's also worth noting that ethanol is routinely added to regular gasoline's fall/winter blends for non-flex-fuel vehicles to raise the octane.

Finding and Pricing E85 Fuel

The U.S. Department of Energy reports that approximately 3,300 fuel stations in 42 states dispense E85 fuel. The Midwest has the highest concentration.

Minnesota has the most gas stations available with E85 fuel, closely followed by Illinois, Michigan, Indiana, and Iowa.

Flex-fuel offers a lower cost per gallon compared to regular gasoline prices. When writing this article, the AAA national average gas price per gallon of E85 is $2.65, or 51 cents less than regular unleaded gasoline.

The Future of Flex-Fuel

The new vehicle market has slowly turned away from E85 fuel compatibility since the Renewable Fuels Association has switched its focus to changing the regular gasoline formula from 10% to 15%.

The EPA has approved E15 for use in all vehicles with model years after 2001; however, not all automakers have shared encouragement for the fuel mixture for that long.

For instance:

  • All GM cars have been E15 compatible for nine years.
  • All Ford cars have been E15 compatible for eight years.
  • But Mazda, Mercedes-Benz, Mitsubishi, and Volvo still don't recognize E15 as an approved fuel in their owner's manuals.