FAQ: Everything You Need to Know About Switching to E85

E85 conversion
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FAQ: Everything You Need to Know About Switching to E85

The subject of converting your vehicle to flex-fuel or E85 gasoline comes up a lot. Although E85 has advantages over standard E10 or non-ethanol gasoline, it also presents some disadvantages. We’ll go through the most frequently asked questions concerning switching to E85 to help identify where you will need to upgrade components for the switch.

Does E85 burn more volume than regular gasoline?

Yes. Most E85 cars require 30-40% more fuel flow compared to a regular gasoline fuel system. Using that extra volume of fuel means your fuel tank won’t last as long as before.

Does E85 have the same energy as regular gasoline?

No, E85 does not. It has approximately 26-28% less energy per gallon compared to regular E10 or non-ethanol gasoline.

What octane rating does E85 have?

Regular gasoline can be found at the pump with 87 to 94 octane available depending on where you are in the country. E85 typically has an octane value of ~104.


Is E85 gasoline cheaper than regular gas at the pump?

In most cases, E85 can be found at a lower price at the pump.

What components are required to make the switch to E85 gasoline?

Due to the extra fuel volume required, you will need at minimum a fuel pump that can pump the required extra volume, fuel injectors that can also handle the extra volume, and a re-tune of your engine management system (basically re-flash your Engine Control Module) to accommodate the larger volume of fuel.

While the minimum components will get you off on the right foot, many of us want to add more horsepower and torque to our vehicles. Beyond the fuel pump, injectors, and computer re-flash, you should add other supporting components that will flow the required fuel amount to meet your goals.

If your vehicle has a fuel pump that is rated at 100LPH (liters per hours), you may choose to replace it with a 255LPH pump instead of the minimum 155LPH pump E85 will require. You can also increase the size of the injectors equally, plus replace your fuel regulator, fuel filter, fuel lines, and fuel pump wiring for the extra required fuel flow. 

Here are some of the Quantum Fuel System fuel pump options:

Part NumberPart DescriptionApplication NotesHorsepower Support
QFS-344FT265LPH E85 IN-TANK EFI FUEL PUMP Universal500
QFS-342FT340LPH E85/FLEX IN-TANK EFI FUEL PUMP Universal, can be doubled for 900+ hp640
QFS-343FT340LPH E85 INTANK FUEL PUMPUniversal640
QFS-353FT340LPH E85 INTANK FUEL PUMPUniversal640
QFS-606FT380LPH INLINE EXTERNAL E85 FUEL PUMPUniversal, external mounting716
fuel pump horsepower

Can any vehicle run E85 gasoline?

The complete fuel system must be prepared for E85, even though any car can run on E85 gasoline. Ethanol is corrosive to most fuel system components. The United States has incorporated 10% ethanol into gasoline since the late 1970s, but higher levels of ethanol weren’t prevalent before 2008.

Unless the fuel system components and computer system are prepared for a higher ethanol content, we should assume that any vehicle before 2008 cannot run on higher ethanol content than 10%. We recommend that you prepare each fuel system component, or at least verify that your current system can handle a higher ethanol content, before switching to E85. 

Can I store my vehicle with E85 in the gas tank?

For some drivers that face extended winter cold months, they have to put their vehicles in storage. That requires preparing the fuel system to sit for a period of time. Ethanol is hygroscopic, meaning it absorbs water.

E85 is very hygroscopic, meaning it can absorb a large number of water molecules that can corrode fuel system components. You can store E85 in the fuel tank of your vehicle, but you will need to add a fuel stabilizer specifically designed for E85 to protect against its added hygroscopic properties.

Is E85 more prone to pre-ignition or detonation?

Yes, E85 is more likely to ignite before the piston reaches near the top dead center and the spark plug ignites the fuel due to the higher ethanol content. This can be compensated for with the engine management computer re-flash and potential colder spark plugs. 

Does E85 Reduce Gas Mileage?

Yes, it can reduce gas mileage. E85 requires 30-40% more fuel volume compared to regular gasoline. That means you can expect your fuel mileage to be reduced by approximately the same 30-40%.

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Does E85 gasoline harm catalytic converters?

No, E85 won’t harm your catalytic converters.

Is it worth it to switch to E85 gasoline?

This answer is very subjective. It can be worth the switch depending on why you are interested. The higher octane levels can be an added bonus for making more horsepower and torque, but the switch also comes with a cost for replacement parts and labor.

If you are already upgrading or building a fuel system from scratch, it may be a good option to make it all E85 compatible from the beginning. If you just want to make your vehicle E85 compatible with cheaper gas at the pump, you may find the cost of parts and labor too high to recoup the savings.

Need help switching to E85?

We continuously receive questions about switching to E85 or making a particular vehicle flex-fuel capable. The temptation of higher horsepower always lures, but you should only make the switch if you intend to incorporate changes that enable the entire system to be E85 compatible.

You should not assume that only a fuel pump, injectors, and a computer re-flash are all that is required. Double-check every component in the system before deciding to make the switch. If you have any doubts, or just need an expert to weigh in on your options, contact us at Quantum Fuel Systems.

You can order a better-designed replacement pump or complete assembly from Quantum Fuel Systems, Monday through Friday, 8:00 a.m. to 5:00 p.m. PT, over the phone or browse our extensive catalog.

For over 15 years, Quantum Fuel Systems has been manufacturing and distributing fuel system components for OEM and performance applications. Our mission is to manufacture fuel systems that are centered around longevity, accurate flow data, and hassle-free direct fitment.

Be sure to snap a few pictures during and after the installation of your E85 fuel system, or if you are a video creator, send us a link to your video on our ‘Submit Your Ride’ page. We love to see what you’re working on and hear about your experience.