Will Flex Fuel Damage My Engine? (Answered)

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Often time, you’d hear non-FFV drivers ask, “will flex fuel damage my engine?” This is a double-barred question, which implies that it has two correct answers – “YES” and “NO.” The answer totally depends on the type of engine your vehicle comes with.

Flex-Fuel may, or may not harm your engine. In other words, if your vehicle is E85 compatible, you can run with flex-fuel without bothering about anything. But, if your car is designed to drive with gasoline or diesel only, filling flex fuel into the tank can cause catastrophic damages.

What is Flex-Fuel?

Flex-Fuel, commonly denoted with E85, is a renewable fuel with high ethanol – up to 85% ethanol content and 15% gasoline or any other hydrocarbon, depending on the need. Notwithstanding, flex-fuels may have ethanol content below 85% for some special purposes.

Basically, flex-fuels are recommended for engines that are compatible with blended fuels. An engine that uses flex-fuels can also use regular gas because they are designed to run with only ethanol gas, regular gas, or a blend of ethanol and regular gas – just don’t put diesel into the tank.

While regular gasoline would work well on E85 engines, if the coin the tossed the other way round, would E85 work well on regular gas engines?

See Also: Can You Mix E85 and Premium Gas?

Will Flex Fuel Damage My Engine?

As highlighted in the introduction, the answer to this question goes two ways. Flex-fuel may damage your car’s engine if the engine is built to run with only diesel or gasoline. On the other hand, flex-fuel won’t cause any harm to your engine if the engine is E85 compliant.

So, to put in proper form, flex-fuel would damage regular gasoline engines, but won’t trigger any clause in an E85 compliant engine.

That said, you should first discover the type of engine your car has; is it an E85 complaint or meant to use only gasoline/diesel? Your answer to this query is the answer to the question, “Will flex-fuel damage my engine?”

The reason why flex-fuel may damage some regular ICE vehicles is that the engines in those cars are not designed to resist ethanol. So, the ethanol in the flex-fuel can corrode the metallic components of the engine, causing expensive damage, and in some cases, irreparable damage.

Well, some drivers go for E85 tune-ups so they can run multiple fuels in their vehicles. If you’re getting an E85 tun up, you’d need to change a couple of things in your engine.

Will Flex-Fuel Hurt a Regular Engine?

No, flex fuel will not hurt regular engine! In fact, flex-fuel is even safer for your engine than regular gas is. E85 contains a high volume of ethanol, up to 83% and as such, apart from powering your engine, E85 flex fuel will also cleans your engine, fuel injectors, and fuel lines.

Does E85 Shorten Engine Life?

Now, this is another point to note. I did mention earlier that E85 contains a significant amount of enthanol, which is good for your engine. However, you must also understand that ethanol is corrosive on fuel-system components, aluminium, rubber, and magnesium.

This means that running E85 on older model car engines without replacing some components, such as fuel pumps, fuel hoses, gaskets, throttle bodies, fuel filters, seals, fuel injectors, etc., will ruin the engine shorten the engine’s life.

How Much HP Does E85 Add?

The benefits of E85 is generally derived from the higher octane it has. This delivers almost the same benefits you get when using methanol injection in your car.

This means that you can run more spark, which normally implies to getting about 25-50 or more horsepower on a forced-induction car.


Flex-Fuel Vehicles (FFVs) are increasingly becoming popular and E85 gas is gradually getting into various gas stations. This is because flex-fuel vehicles allow a wide variety of fuels you can run with.

The versatility of FFVs is more reason why many people tune up their cars to be E85 complaints. E85 is the commonest flex-fuel variety available. Flex-fuels won’t damage any engine designed to run E85 gas; but if your car isn’t E85 compliant, filling flex-fuel may cause you a lot of expenses.

Will flex-fuel damage my engine? No, it won’t if you’ve got an E85 engine, and Yes, if you drive regular ICEs.

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