What is Flex Fuel – Pros and Cons

Flex-fuel has existed for a long time, and it’s gaining popularity, even so, many people don’t know about it. It is cheaper than regular fuel. Should you opt for a car that uses flex fuel, and why is it cheap? What is flex fuel in the first place?

Whether you want to invest in this type of fuel or you want to know what that new sticker at a gas station means, we got you covered.

Here, you will learn “what is flex-fuel for cars” and its pros and cons. Let’s keep the ball rolling.

What is flex fuel?

Flexible fuel, also known as flex-fuel, is a fuel made of gasoline and ethanol or methanol. So, what is a flex-fuel vehicle? Flex-fuel vehicles are equipped with internal combustion engines that run on one fuel type. Aside from a few modifications, flex-fuel cars are like gasoline vehicles.

These vehicles are not new in the automotive industry. They’ve existed since the early 1990s and have become popular since 1994. It kept making waves, and in 2017, there were 21 million flex-fuel vehicles on the road.

flex fuel

Pros and cons of Flex-fuel

As the saying goes, ‘whatever has a sweet part also has a bitter part.’ Flex-fuel is not an exception to these rules. Let’s look at the pros and cons of flex-fuel.


Here are some benefits you’ll derive from using flex-fuel cars.

Improved performance: While some mechanics and motorists may argue that using alternative gas will negatively affect your car’s overall performance, that’s not always true. It can increase vehicle performance. Flex-fuel vehicles do not suffer performance issues when running with E85 fuel. Sometimes, it even leads to increased torque and horsepower.

You may wonder, ‘what is E85 fuel’. It is a fuel type with 85 percent of ethanol and 15 percent gasoline or another hydrocarbon.

Tax benefits: Motorists who drive flex-fuel vehicles receive tax benefits to eliminate or reduce their tax obligations.

Tenably produced: Many flex fuels run on ethanol, which is tenably produced from products like corn and sugarcane. These ingredients make ethanol an excellent alternative to foreign oil.

Good burning facility: One of the essential merits of owning a flex-fuel vehicle is its good fuel burning rate. It can burn whatever volume of gas that enters the combustion chamber. The vehicle features electronic car sensors and microprocessors that gauge the blend and adjust gas injection and timing.

Cleaner for the environment: Nowadays, many people are much concerned about the effect of fuel consumption on the environment. Flex-fuel burns cleaner than gasoline because of its ethanol composition in it. And this makes it release fewer emissions into the atmosphere.

Advanced technology: According to an article by Car Bibles, flex-fuel vehicles are built with advanced technology, such as electronic car sensors. These advanced technologies send accurate readings to the car computer and allow the vehicle to adjust to the way it’s operating. Flex-fuel contains 10-85% ethanol. Lastly, these advanced technologies will determine the most efficient blend proportion of the vehicle.


Of course, flex-fuel has some demerits you should consider before investing in these vehicles. Here are some of them.

Possible engine damage: You may ask, will flex-fuel damage my engine? Indeed, you want your engine clean and free from sludge deposits. But ethanol absorbs dirt easily, which can cause corrosion on the internal engine components and lead to engine failure.

Gas Mileage: Motorists have a major concern about flex-fuel gas mileage. While some experts say the gas mileage is relatively similar to regular gas, others say it differs from regular gas.

Ethanol raises a vehicle’s octane level, but it contains less energy. Simply put, it takes flex-fuel more time to produce the same energy level as regular gas. Therefore, flex-fuel will give fewer miles per gallon than regular gas. Flex-fuel prices are cheaper than regular gas, which may balance the fewer miles per gallon.

Sole crop use: We discussed above that flex fuels are produced with corn and sugarcane. This can be a disadvantage. Crops allocated for flex-fuel production can’t be used for other purposes. This can hike the price of animal feeds. It will also affect fuel production during poor corn harvest. 

Fewer gas station: Since the number of flex-fuel vehicles on the road is lesser than regular gas vehicles, fewer gas stations have flex-fuel pumps. In fact, only a fraction of gas stations carries ethanol fuels. Hopefully, that is likely to change as more consumers buy flex-fuel vehicles.

However, with modern flex-fuel engines, you have the option to use any combination of gasoline and ethanol. You can use 85% ethanol or 100% unleaded gas. The advanced electronic car sensors will detect the fuel combination in the tank and make the necessary adjustment.

what is the benefit of flex fuel

What Is The Difference Between Flex-fuel And Regular Fuel?

Here are the differences between flex-fuel and regular gas.

Purse control

Ethanol produces less energy than gasoline-only fuel. This means an engine needs more ethanol in the combustion chamber to produce the same energy as regular gas.

Flex-fuel vehicles have a higher purse range in the fuel injection, allowing an extra 40% liquid fuel in the air-fuel mixture ratio. The advanced electronic car sensor can detect the amount of ethanol and allow a proper fuel mixture for a better concentration.

Fuel system components

Ethanol has more corrosive agents than gasoline. This means that it corrodes internal engine components. However, automakers are fighting this downside to ethanol.

That’s why you won’t see rubber, aluminum, or magnesium parts inside the fuel tank. Instead of using terne-plated steel for producing gas tanks, automakers use stainless steel material. And the fuel lines feature plastic-lined stainless steel.

Extra features

Since ethanol is conducive, meaning they carry electricity flow, auto manufacturers added extra safety measures. For example, automakers include safeguards against arcing design for tank-mounted fuel pumps.

The next is water contamination in ethanol, leading to high formic acid in the combustion chamber. To prevent causing catastrophic damage in the combustion chamber, automakers recommend using acid-neutralizing engine oil.

What cars take flex-fuel?

General Motors is the brand with the most E85-friendly vehicles. Other notable vehicle makes and models include Chevy Impala 3.6L, Silverado 5.3L 4WD and RWD, Suburban/Tahoe 5.3L 4WD, and RWD. The next is the Ford vehicles. We have Ford explorer 3.3L AWD, Ford Transit T-150 3.5L, AWD, RWD, F-150 3.3L V6, 5.0L V8, RWD, and 4WD. Transit connect 2.0L van, wagon.


Q: Can you use regular gas in a flex-fuel vehicle?

Yes, you can use regular gas in flex-fuel vehicles without incurring damages. The flex-fuel engine is designed to run efficiently on ethanol and other fuel types. Whether you have gas blended with methanol and ethanol, or regular gas, put it in the flex-fuel vehicle. It’s all going in the same tank.

You may ask, what is a flex-fuel engine? Flex-fuel engines are vehicle engines on FFV. You can research how these vehicles work for a better understanding.

Q: Is flex-fuel gas or diesel?

Flex-fuel, also known as flexible fuel, is a type of fuel combined with gasoline and methanol or ethanol. Vehicles running on this fuel type are designed to be fed more than one fuel. Flex-fuel also offers various merits over conventional diesel or gasoline options.

So, is flex-fuel gas or diesel? Flex-fuel comprises gasoline and ethanol. Therefore, it is gas and not diesel.

Q: Can you put diesel in a flex-fuel?

No. Diesel fuels are not compatible with any engine aside from diesel engines. Diesel differs from gasoline and ethanol fuels and will not work in their place. A critical example is, if you pour diesel into a gasoline engine, it’ll not run.

Can you mix E85 with regular gas in a flex-fuel vehicle?

Yes. As long as you’re driving a flex-fuel vehicle, mixing E85 with regular gas will not cause any problem. A computer in the flex-fuel vehicle will adjust the fuel blend up to 85 ethanol. However, you may notice a reduction in miles per gallon and acceleration depending on the E85 you mixed.

Q: How much does a flex-fuel kit cost?

What is a flex-fuel kit, anyway? A Flex-fuel kit is a kit that controls the fuel injection process. It controls each of the injectors separately to provide optimal fuel flow. It works pretty fine on various fuel injection approaches.

Converting your gasoline to a flex-fuel vehicle will take around 15 minutes. The flex-fuel kit will cost around $365 to $500. However, this kit works fine on vehicles that use both fuel port and electronic fuel injection via the engine control module.

Q: Is flex-fuel cheaper than regular gas?

Flex-fuel is cheaper per gallon than gasoline but a bit costlier than gasoline per mile. As explained above, ethanol fuels have less energy content than gasoline. That makes it consume more gas when driving. Therefore, as flex-fuel costs less at the gas station, the decrease in MPG makes it costlier than regular gasoline.

Q: What if I accidentally put flex-fuel in my car?

If you accidentally put flex fuel in your car, do not panic. While the check engine light may illuminate the dashboard, it won’t cause any harm to your vehicle. You’ll be fine until the fuel burns out of the gas system. You won’t want to run out of gas on the road. So, top up your tank when the low fuel light comes up on your dashboard.

Final words

At this juncture, we’ve cleared the air on the subject, ‘what is flex-fuel?’ The debate on the pros and cons of flex-fuel is disappearing soon. However, there seems to be a significant switch from regular gas to flex-fuel vehicles. 

The number of ethanol refining plants is increasing daily. So, even if it’s not what you want yet, weigh the pros and cons and compare it with regular gas. The automotive industry keeps evolving. Though we don’t know what the future holds for us, we can guess from observing the signals.

Osuagwu Solomon

Osuagwu Solomon is a seasoned automotive technician for the past 9 years, and a technical writer. He loves writing about auto professional repair guides, DIY repair guides, and buyer’s guide. After spending six years in the automotive workshop, he decided to impact his knowledge to people aside his domain, and he has achieved this by centering his Automotive writing skills on REPAIRS.

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