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Does Ethanol Reduce Your Gas Mileage?

Updated on February 9, 2014
The advertisement from a local chain of filling stations for ethanol treated gasoline, also known as E10.
The advertisement from a local chain of filling stations for ethanol treated gasoline, also known as E10. | Source

America's Fuel

A local gas station chain markets their regular unleaded gasoline as ethanol enhanced. The use of the word “enhanced” is curious because it implies that there is some benefit or advantage to choosing this gasoline over other available products. Messages on the pump further add that this is “America’s Fuel” and that it may contain up to 10% ethanol. This ethanol modified product is commonly called E10.

As an alternative the chain also offers an ethanol free 87 octane product called PureMax, which is an interesting name in its own right. Another gas station just down the street calls their ethanol free fuel "Pure Gas" and proudly advertises that it will improve your gas mileage by 25% over ethanol grades. Pure gas is typically more expensive than E10 with the same octane rating. For example, during my last visit the E10 cost $3.299 per gallon while the PureMax was listed at $3.679 per gallon. Since I ended up buying 11 gallons the E10 saved me around $4. At first glance the obvious enhancement imparted by the ethanol addition is to the upfront cost of filling your tank.

A sign at a local gas station touts the supposed benefits of ethanol-free pure gas.
A sign at a local gas station touts the supposed benefits of ethanol-free pure gas. | Source

Regular unleaded gasoline "that may contain up to 10% ethanol" is also known as E10.

Based on the unit price it seems obvious there is an initial savings benefit to choosing the E10 ethanol treated gasoline. However, do you really see a financial benefit when all is said and done? Ethanol has about 25% less energy content than gasoline, so adding this substance dilutes the ability of the fuel to fire the pistons and gives your engine less bang for the buck. Consequently, due to this energy density reduction, there is a chance you will actually get fewer miles per gallon if you choose the ethanol enhanced fuel over an ethanol free grade like PureMax. Maybe the banner that proclaims you can save 25% on gas mileage is right.

So, does the ethanol infused E10 provide a financial enhancement over an alcohol free option like PureMax just by being cheaper or is the upfront savings lost due to the inferior gas mileage of the fuel? To get to an answer we need to calculate the number of miles per dollar of gasoline purchased, or miles per dollar (MPD). Just for fun I decided to conduct an experiment to determine the MPD of both the E10 and the PureMax fuels to see if ethanol gasoline can truly be called enhanced or if the "No Ethanol" sign is right after all.

Ethanol Enhanced E10 versus PureMax Pure Gasoline

Gas nozzle for PureMax, a pure gas fuel offered by local filling stations
Gas nozzle for PureMax, a pure gas fuel offered by local filling stations | Source

To evaluate the effect of ethanol on miles per dollar or MPD I decided to run a little study using my own vehicle. I drove my 2008 Subaru Forester for several weeks using the ethanol enhanced 87 gasoline and recorded the mileage and fuel consumption. Then I switched over to the Puremax ethanol free and monitored the same information. I ran the results through a statistical analysis called a two sample t-test to determine if there truly was a performance difference between the two fuels. Finally, I calculated the miles per dollar.

During the experiment I tried to keep my driving habits and patterns as consistent as possible. The driving represents a mix of highway and city driving, mostly on my commute to and from work. If I took a long highway trip on a certain tank of gas I discarded that tank from the study.

Table 1 below shows the results for the E10 gasoline. The average gas mileage came out at 24.2 MPG and based on the recent cost of $3.299 per gallon this gives a miles per dollar or MPD of 7.33.

Using pure gasoline instead of E10 boosted my MPG by 7%, but reduced my miles per dollar or MPD by 4% due to the higher cost per gallon.

Table 2 contains the PureMax test results and shows the gas mileage at 25.8 MPG. With the recent cost per gallon of this fuel at $3.679 it ends up having an MPD of 7.01.

These results show that you can see a gas mileage boost of approximately 7% by using the pure gasoline instead of the E10, but based on current prices you end up getting penalized financially due to the higher cost as shown by the 4% drop in miles per dollar.

Table 1 - E10 Gas Mileage Results

Tank
Miles
Gallons
MPG
1
169.2
7.242
23.4
2
231.1
9.092
25.4
3
196.3
8.132
24.1
4
88.9
3.708
24.0
5
257.3
10.680
24.1
6
211.2
8.741
24.2
Total
1154
47.595
24.2

Table 2 - PureMax Gas Mileage Results

Tank
Miles
Gallons
MPG
1
276.2
11.247
24.6
2
298.7
11.561
25.8
3
294.4
11.063
26.6
4
275.5
10.81
25.5
5
201.0
7.581
26.5
Total
1345.8
52.262
25.8

"The 20 Cents Rule"

If pure gasoline costs 20 cents or more per gallon than E10 than go with the E10, but if the difference is less than 20 cents the pure gasoline is the better value.

The price per gallon for ethanol-free Puremax.
The price per gallon for ethanol-free Puremax. | Source

The Bottom Line

My experiment showed that using ethanol enhanced E10 fuel instead of the ethanol free PureMax reduced my MPG by 6.2%, from 25.8 to 24.2 miles per gallon. However, because of its higher cost the PureMax actually delivered 4.4% less MPD than the E10, 7.01 versus 7.33 miles per dollar, and turned out to be the worse choice from a cost perspective.

This financial benefit, however, depends on the price difference between the two grades. As the pure gasoline price approaches the E10 cost a crossover point is reached where it actually becomes the better value in terms of MPD. With the results of this study I came up with a guideline called “The 20 Cents Rule” that is easy to remember. It states that if the ethanol free option costs 20 cents or more per gallon than the E10 than go with the E10, but if the difference is less than 20 cents then pure gas is the better value.

The other thing I learned is that you can't always believe what you read on advertisements since the pure gas delivered only a 7% increase in MPG instead of the "up to 25%" written on the banner. However, because of the lower overall cost of the ethanol enhanced E10 the ethanol does appear to provide a financial "enhancement" to the consumer.

My 2008 Subaru Forester averaged 24.2 miles per gallon with E10 for mixed city/highway driving.


Prices for the ethanol treated varieties of gasoline.
Prices for the ethanol treated varieties of gasoline. | Source

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    • profile image

      Tom 2 months ago

      MTBE vs Ethanol vs Tetra-Ethyl Lead -- all used to oxygenate gasoline -- all are used to "lean out" your fuels combustion- which when pure gasoline is used is too high causing pinging.

    • profile image

      country boy 6 months ago

      That answers my question why my vehicle will do 4 mpg better without the ethanol.

      Now I know why my lawn equipment won't start after sitting for months. Mechanics have informed me to use pure gas.

    • theframjak profile image
      Author

      theframjak 2 years ago from East Coast

      Hi Dressage Husband, Thanks for reading. I'm glad to hear you liked it. You bring up a good point with the long term effects of E10 use on engine components. I'm sure this also has financial consequences on the overall use of this fuel compared with the pure gas alternative. Thanks again for stopping by.

    • theframjak profile image
      Author

      theframjak 2 years ago from East Coast

      Hi purl3agony, thanks so much for reading my HOTD. I never thought I would get one, but it finally happened! I'm glad you found it to be useful.

    • theframjak profile image
      Author

      theframjak 2 years ago from East Coast

      Hey drpennypincher, thanks for reading. You're so right, there are a lot of other factors that can come into play and affect the results, which makes these experiments so challenging. Thanks again for stopping by.

    • theframjak profile image
      Author

      theframjak 2 years ago from East Coast

      handymanbill, thanks so much for reading and sharing the interesting information about ethanol fuel. I had heard about this in regards to my lawnmower but didn't consider that it would also be true for my car.

    • Dressage Husband profile image

      Stephen J Parkin 2 years ago from Pine Grove, Nova Scotia, Canada

      I really liked this Hub and the way you derived the actual miles per dollar spent. This is the only criteria for most users to be concerned about. The only factor not mentioned is any effect on the life of engine components and servicing costs. I am not sure what the long term affect of using ethanol would be if this was taken into account.

    • purl3agony profile image

      Donna Herron 2 years ago from USA

      I appreciate you collecting this data and doing the analysis for all of us. I know if I want to be a responsible driver, I should be noting and charting my gas consumption, but I never do. Thanks for this easy to understand comparison of the potential value of ethanol gas. Congrats on your HOTD!!

    • drpennypincher profile image

      Dr Penny Pincher 2 years ago from Iowa, USA

      I like how you did experiments and presented your data. Hard to argue with that. The difference in mpg is subtle enough that small differences in driving, such as having a passenger or a bit of extra city driving can make it hard to see the difference in mpg between pure gas and ethanol. But collecting data from multiple tanks makes it easier to see the trend. Nice work.

    • handymanbill profile image

      Bill 2 years ago from western pennsylvania

      what is really an interesting fact also not even talked about here. Is that the shelf life of Ethanol gas is far less then the shelf life of regular gas. That is why in cools weather you should keep your Tank full. If you do not then the gas with Ethanol will possibly have water condensation in it. Also it is hard on your car engine.

    • theframjak profile image
      Author

      theframjak 4 years ago from East Coast

      Thanks for reading m. I think our two rules are close enough to support each others finding.

    • profile image

      4 years ago

      Good post. I did a strictly numeric analysis that came up with a similar result. Ethanol has 34% less energy density than gasoline. My break even number at an E10 price of $3.41 is $3.53 for pure gasoline so it is closer to a 15 cent rule in a purely theoretical world. Either way, wohosr is right and that doesn't even include the increased cost of corn tortillas.

    • theframjak profile image
      Author

      theframjak 4 years ago from East Coast

      wojosr, you raise a good point. Like so many other things, there are often underlying costs associated with things that are not apparent at first glance or get buried. Thanks for reading.

    • profile image

      wojosr 4 years ago

      Based on your test and my personal mpg records when gas was still available in addition to E10 it shows that rather than reducing the amount of oil the country is using we are using the same or more than after the gov. required the use of ethanol as an additive to gas. Oil is delivered to the refineries by pipeline whereas the ethanol uses trucks to bring corn to ethanol refinery then ships the ethanol to the refineries to add to gas which consumes fuel and then we experience lower mileage which means we use almost the same amount of gas as before E10 and the additional fuel required to produce and deliver ethanol actually increases the oil needed in the country.

    • theframjak profile image
      Author

      theframjak 4 years ago from East Coast

      Monis Mas, Thanks so much for reading and thanks for the enthusiastic response. Hopefully, your husband will also find it interesting.

    • theframjak profile image
      Author

      theframjak 4 years ago from East Coast

      toknowinfo, thanks for reading and thanks for the complement. I'm glad you enjoyed the articles.

    • Monis Mas profile image

      Aga 4 years ago

      Awesome hub, I am sharing with my husband!

    • toknowinfo profile image

      toknowinfo 4 years ago

      Great article. It explains why the oil companies use ethanol, which is a corn derivative, and more expensive to produce than oil. Knowledge is power, so thanks for the great info. Voted up and more and sharing and putting it on twitter.