Where E85 Ethanol is available (not very common), the price per gallon is often lower than regular unleaded gasoline. Though I've read that fuel economy is commonly reduced by 20% or more, when using E85 Ethanol.

I'm driving a flexible fuel vehicle; so it can run on either fuel, but I'm not sure if I can actually save money by switching to E85.

Is it possible to reduce fuel costs by switching to E85, or is it better to stick to good ol' gasoline?


This is an easy experiment to do:

  1. Fill your tank with unleaded.
  2. Drive a well-known standard route. For example, my commute is almost always the same from day to day.
  3. Drive to gas station and re-fill the tank with unleaded. Note amount filled and cost.
  4. Take the total miles driven from steps 1 - 3 and divide by the number of gallons filled in step 3. That's your miles per gallon (bigger is better).
  5. Take the total miles driven from steps 1 - 3 and divide by the cash paid in step 3. That's your miles per dollar (bigger is better).
  6. Repeat steps 1-5 until you feel like you have a good data set for unleaded fuel.
  7. Now repeat steps 1-6 except that everywhere you see "unleaded", put "E85."

By this point, you should be able to conclude whether the economics are recommending a particular fuel.

Later, you can consider the ecological and emissions impacts of the two fuels and make your own choice.

  • 2
    I was sort of hoping there might already be some impartial study data available. Testing this myself seems clumsy and error prone.
    – Tester101
    Apr 28 '12 at 13:13
  • 4
    I don't think that it's clumsy and error prone - I think Bob's suggestion is the only way to find out if you can save money using E85 or not. There are too many variables that come into play which influence your particular fuel consumption that a "generic" study cannot take into account. Apr 29 '12 at 15:27
  • 1
    @Tester101, testing yourself is the only way to truly confirm a claim of efficiency. The way I set up the procedure, you're hitting the gas station pretty often but you'll have solid data quickly.
    – Bob Cross
    Apr 30 '12 at 12:56
  • 1
    There have been studies (sorry, no links) that show there is 20-30% mpg decrease due to the less energy-dense E85 mix. This would need to be compared with the price difference between E85 and your standard fuel.
    – Patrick
    May 8 '12 at 16:49
  • @Patrick, exactly: that's the point of step 5.
    – Bob Cross
    May 24 '12 at 12:35

I would like to point out that E85 has a lower energy density than gasoline. Therefore, although you are paying less per gallon of fuel, you may be paying an equivalent amount (or more!) per, say, kilo-Joule of energy. This can easily be verified using the above-posted experiment. Additionally, Wikipedia states that E85 has 33% less energy content than gasoline. So, assuming equivalent efficiency for both fuels (which realistically is rather unlikely) you would need to see at least a 33% drop in the price of E85 in order to see a net benefit.


From the tests that I've seen, E85 gets less MPG. Here are a couple:

An interesting fact about E85 that not all people know is that it's more resistant to detonation so some high performance enthusiasts will use it to extract more power out of their cars.


For those of us who don't like running experiments ourselves, and would prefer to look at others data. This type of information is available at Fuel Economy.gov. If you click the Find a car link, you can select your vehicle and get all sorts of EPA data.


One way to search for this data is to use site like Fuelly.

We can search Google for the following query “E85 site:fuelly.com”. There we get results that point mostly to fuel-up logs tagged with “E85”.

For example, we can pick one of the results, and see E85 fuel-ups of someone’s 2010 Chevrolet HHR with flex L4. Then we can compare those with their other fuel ups (checking notes for references to style of driving, highway v. city etc.), and with other flex-fuel Chevrolet HHRs registered on the website.

So, it would take some homework, but chances are your vehicle is already there, and there is some data available.

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