From the the documentary Pump at 1:07:

NARRATOR: But what if we don't need a flex fuel car or even a kit? What if the car you drive today already contained the technology that could enable it to run on gasoline, ethanol, or methanol? What if the only thing that prevent that from happening was a simple software update of the car's computer?

DAVID BLUME: I've been on the assembly line at Ford, I've gone from the start of the fuel system at the tank, all the way to the fuel injectors. There's not a single item that is different between eh alcohol version and the non-alcohol version. And at the end of the process, I asked the guy: "What's different? W haven't seen any differences so far in parts." He goes, "Oh, its the software."

It then says that people will be able to hack cars to give them fuel choice before switching to this clip:

In America right now, we are under the impression that you have to change a ton of parts to make this run off alcohol fuels. That is not true. The software solutions have been developed already.

Every car sold in the US since 1996 has what's called an OBD2 plug. [...] You can actually reprogram the car.

Now, here's how I discovered all these cars have flex-fuel.

[... shows using a diagnostics program on a laptop connected to the car to change a setting ...]

It can either calculate it, or it can use an actual sensor. I don't want to add a sensor. I'm just going to have it calculated. So I just turned it on, and started going for some drives. And it adapted to the fuel.

Is it true that all, or almost all, new gasoline cars in the United States can run on E85 with no hardware modifications at all, with only a software update?

  • @Oddthinking, I was referring to the claim that even cars that are not marketed as flex-fuel vehicles are able to run on ethanol.
    – user29977
    Nov 21, 2015 at 22:23
  • Welcome to Skeptics, @zagadka314. I've only watched the trailer, not the full documentary. Based on that, I strongly suspect they are referring to flex-fuel cars. But if people made claims about this in the documentary that are not in the trailer, please provide a transcript of that claim. That was we can be sure we aren't arguing against a strawman claim.
    – Oddthinking
    Nov 21, 2015 at 23:40
  • @Oddthinking I have something better: a video clip! youtube.com/watch?v=N6kPJXbPb40
    – user29977
    Nov 21, 2015 at 23:55
  • Great. Transcribed.
    – Oddthinking
    Nov 22, 2015 at 1:28
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    User who doesn't know what they are doing looks into a software configuration they are not supposed to look at and change a setting they are not supposed to change. I have seen many disasters starting that way. Maybe his car runs now, but the question is if it will still be running after a few thousand km.
    – Philipp
    Nov 22, 2015 at 11:36

1 Answer 1


There are close to 17.4 million Flexible Fuel Vehicles on US roads.

All gasoline vehicles in use in the U.S. today can accept gasoline blended with up to 10 percent ethanol (sometimes called gasohol). Flexible Fuel Vehicles (VVFs) are cars and trucks that can use any level of ethanol up to 85 percent. They're built with special fuel system components designed to be compatible with higher ethanol concentrations.

Flexible fuel vehicles are identical to gasoline-only models except for a few engine and fuel system modifications.

FFVs experience no loss in performance when operating on E85, and some generate more torque and horsepower than when operating on gasoline. However, since ethanol contains less energy per volume than gasoline, FFVs typically get about 15%–30% fewer miles per gallon when fuelled with E85.

The E85 component modifications also changes from company to company. For example in Vortec 5.3L Gen IV V-8 engines used in General Motor cars, only the fuel rail and fuel injectors are different between E85 versions and non-E85 version.

A new virtual fuel sensor reduces the cost and complexity of adding E85 capability to the fuel system. The ECM samples the exhaust at the oxygen sensor, and an algorithm determines whether E85 is used, as well as its mixture percentage with gasoline. It’s a much simpler, less costly system than previous systems that relied on fuel composition sensors. In fact, the entire system on the engine is simple: only the fuel rail and fuel injectors are different between E85 versions and non-E85 versions.

Technically, a non-flex fuel model can be modified to run on E85, but it is not cost-effective since several parts of the FFV fuel delivery system needs to be modified to be made E85 fuel compatible.

The significant difference is the fuel sensor which detects the ethanol-to-gasoline ratio. A number of other parts on the FFV’s fuel delivery system are modified to be E85 compatible. The fuel tank, the fuel lines, fuel injectors, computer system and anti-siphon device have been slightly modified. Alcohol fuels can be more corrosive to certain metals than gasoline; therefore, fuel system parts have been upgraded for high level ethanol use.

There are EPA certified kits for converting conventional gasoline-fueled vehicles to run on E85 fuel.

Pure ethanol (100% ethanol or E100) could theoretically be used to power flexible fuel vehicles (FFV) however not used for the following stated reasons.

  1. Ethanol is bad for cold-starting, because it doesn’t burn as quickly as gasoline. (It has a higher octane, if you’re interested.) Pure ethanol would be useless as fuel in the winter months.

  2. There are no passenger cars designed to take E100 (but some racing cars are) so it could damage your car engine. Even Flexible-Fuel vehicles (FFVs) – which can run on petrol or ethanol – can only take up to E85.

  3. We have many people using E98 and E100 in their converted vehicles. Every car is different so you will need to play mad scientist and experiment with the water content. Too much water displaces the oxygen in the cylinder resulting in an anti-dentonant. Not enough water then results in wasting fuel. The E85 Conversion kit manufactured by Fuel Flex International FFI was featured in the movie PUMP.

Flexible fuel vehicles have an internal combustion engine capable of operating on gasoline, E85 (a gasoline-ethanol blend containing 51% to 83% ethanol), or a mixture of the two. FFVs' which are considered alternative fuel vehicles (AFVs) have one fueling system, which is made up of ethanol-compatible components and a powertrain controller calibrated to accommodate the higher oxygen content of E85. The fuel system components are described here.

North American and European flex-fuel vehicles are optimized to run on E85, a blend of 85% anhydrous ethanol fuel with 15% gasoline to reduce ethanol emissions at low temperatures and to avoid cold starting problems during cold weather. There is a winter blend of E70 in the U.S. from November until March. Technically, a non-flex fuel model can be modified to run on E85, but it is not cost-effective.

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    @Oddthinking-will try to change the answer based on your inputs and thanks for your suggestions! Nov 23, 2015 at 11:39
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    @zagadka314 It does answer the question--hardware changes are needed because the E85 is more corrosive than gasoline. You need to build the fuel system out of parts capable of withstanding this. Nov 24, 2015 at 5:19
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    I wonder about the Ford and if the parts are actually different in any way. I also wonder about the "flex fuel" software update. Do you think these are questions that could even be answered? I don't understand how a documentary can make such a massive claim without much evidence. Yeah, the Blume guy is nice, but they should have some evidence. Why not look at the parts list for both cars and show they are the same? List the parts: "Fuel pump… The same. Fuel line… Same. [Insert sensor here]. Same"
    – user29977
    Nov 25, 2015 at 2:30
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    @zagadka314 Since they make some E85 vehicles they might simply be making all the parts out of materials that can take it--a slightly more expensive part being cheaper than having two different parts. Nov 25, 2015 at 21:24
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    @LorenPechtel That could well be true, but then that would imply the claim itself is true… I don't think we can trust them without evidence and they just haven't provided it.
    – user29977
    Nov 26, 2015 at 1:34

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