Ethanol Efficiency

Living in Iowa, it’s hard to avoid conversations about ethanol. And working for an advertising agency that previously represented the ethanol industry and continues to represent ethanol-related businesses causes the topic to come up in conversation for me more often than for the average Iowan even. I use ethanol in my car, as does most anyone who hasn’t put much thought into it. It’s commonly six cents cheaper. Who wouldn’t go with six cents cheaper?

Well, I’ve talked to a few people who wouldn’t go with six cents cheaper. Their logic comes down to efficiency. While ethanol is cheaper, it actually takes your car more ethanol to produce the same amount of energy, so you’re getting few miles-per-gallon with ethanol vs. standard unleaded gas. “Meh,” I told myself, “that’s a worthwhile tradeoff for a cleaner planet.” Then the ethanol dissenters typically suggest that the process of creating ethanol actually creates more pollution. After a few of these conversations, I decided to do some testing and find out the truth by the numbers.

82% of statistics are made up, so I set out to make up my own, in the only context that matters to me: my own car, a 1997 Buick LeSabre. Lacking the resources to test the pollution from my car (much less the processing plant at which my ethanol was produced), I decided to test what I could: the fuel efficiency of ethanol. Over the past couple months I’ve been recording all of my gas purchases, as well as my mileage between them.

The process of figuring out miles-per-gallon was actually a bit confusing to me at first, so I’ll explain it here. When I fill up my tank, I reset my trip odometer. On my next refill, I know how many miles I’ve gone while emptying my tank, and the amount I put in to refill the tank is equal to the amount of gas I must have used while traveling those miles, because a full tank is always the same size. So by dividing those miles by those gallons, I have a miles-per-gallon number.

This gets confusing when testing different types of gas, because the number of gallons on my current fill-up is actually the number of gallons used with the previous fill-up’s type of gas. I repeated this process several times, and attempted to get as close to a full tank as possible to avoid the previous tank skewing the efficiency of the current tank as I switched back and forth between 10% ethanol and 0% ethanol unleaded gas.

So that’s my methodology. Here are the numbers:

Ethanol % Gallons Miles Highway/City Miles-per-gallon
10% 15.056 393.7 Highway 26.149
0% 15.488 359.2 Highway 23.192
0% 14.571 257.0 City 17.637
0% 15.813 416.6 Highway 26.345
10% 14.923 370.3 Highway 24.814
0% 11.318 293.5 Highway 25.932
0% 16.497 371.0 City 22.488

Notice that I added a Highway/City driving variable to the data. I quickly noticed that my numbers weren’t nearly as steady as I was expecting, and I believe my hunch that this variance is primary due to highway vs. city driving is borne out by the numbers above. So the first conclusion is that any variance in efficiency between ethanol and non-ethanol gas is much smaller than the variance between city and highway driving. Those of us concerned about fuel-efficiency need to be working to make our cities more hospitable to walking and biking more than we need to be debating the merits of ethanol. Nonetheless, on to debating the merits of ethanol.

It’s clear to me from the numbers above that ethanol is indeed less fuel efficient than non-ethanol gas in my car. However, the difference is very slight, and it is more than offset by the standard price difference of six cents per gallon. Figuring that in, the average miles-per-dollar figures (for highway miles only, as I’m still finishing my tank of city-driving ethanol) are: 12.74 for ethanol and 12.21 for non-ethanol. So despite the lower fuel efficiency of ethanol, the price difference means that for every dollar I spend, I’m going more miles by using ethanol in my car. With this in mind, I intend to continue using ethanol.

But what about the pollution? Well, I’m not sure about the pollution. I haven’t seen any actual numbers on that, so all I have to go on is what other people say they heard somewhere. Some people say ethanol is better than non-ethanol gas for the environment overall (notably a former client of my employer says this quite often), while others say it’s worse. If anyone has any numbers on this, I’d be interested to see them. But lacking any testable numbers, it seems to me everyone is just arguing whatever reinforces their own beliefs.

And yes, I’m aware that dark forces (e.g. Archer Daniels Midland Company) are at work making corn an artificially prominent part of the American (and increasingly world) economy in everything from ethanol to high fructose corn syrup to construction materials. And maybe when I’ve finished reading Omnivore’s Dilemma this will be enough to convince me to act against my own immediate economic interests. But for now, I’m sticking with the six cents cheaper at the pump and the half a mile-per-dollar more on the road I get with ethanol. As the standard disclaimer says, your mileage may vary, and I’d encourage everyone to do their own testing in their own cars.


Let me tell you my experience computing miles per gallon with regular gasoline and with E10. I drive a compact truck with a four-cylinder engine and a manual transmission.

On several long trips at highway speeds I have carefully kept track of the fuel I burned and miles I drove. I've found I consistently get about 32 mpg when burning gasoline, and about 29 mpg burning E10.

That means on a theoretical trip of 320 miles I would burn 10 gallons of gasoline or 11.1 gallons of E10. But, if I burned E10, 90% of that fuel would be gasoline. What is 90% of 11.1 gallons? A: Just slightly less than 10 gallons.

My experience is that whether I burn gasoline or E10, I wind up burning almost exactly the same amount of gasoline.

I long ago concluded buying E10 cost me more money, and I now buy E10 only if I really need fuel and E10 is all I can find.


Gary Dikkers
Gary, you already told me that story in a previous post. That's part of the reason I did my own testing, and I found that I'm actually saving money despite the minor difference in fuel efficiency, which isn't anywhere near 10% in my car. I don't really care how ethanol works in your truck, as I'm not driving your truck.

It's not clear to me that you even read what I wrote. You seem to be just searching for anything mentioning ethanol and leaving the same comments all over the web. I think you need a new hobby.

Ah, I thought perhaps we had corresponded previously. Yes, I did read your entire post. But what you did doesn't change my results. I first tried my experiment three years ago, and this July during a long trip on a vacation, I tried it again. Got almost exactly the same results -- 32 mpg with 100% gasoline, and 29 mpg with E10. I also have a nephew who commutes about 40 miles daily. He has had lots of opportunities to experiment with both fuels, and his decline in mileage is much what I experienced.

It's not a hobby -- it's a mission. I realize the underpinning matrix of politics, agribusiness, tax credits, subsidies, mandates, and protective tariffs means the corn ethanol bandwagon has gained so much momentum it is almost unstoppable, but a few people have to be like the boy who pointed at the naked king and said, "But look, he's not wearing any clothes." as everyone gasped and told him to be quiet.

Best regards,

Gary Dikkers
Gary, my car's fuel efficiency doesn't change your results, but it draws into question whether your results are unique to your car. Ethanol clearly contains energy. If your vehicle can't extract any energy from ethanol (and by your numbers, it can't), you might want to check what's wrong with your vehicle before you spend much more time telling everyone else what's wrong with their fuel.

What would you say if I offer the results from a really large sample size -- for example the entire State of Minnesota?

As I’m sure you know, Minnesota mandates that all their motor fuel contain 10% ethanol. Perhaps you didn’t know the USDOT keeps statistics on the amount of fuel used and miles driven in each of the 50 states. That of course makes it possible to compute each state's average fuel mileage.

Just for the heck of it I compared Minnesota (with mandated E10) to Wisconsin, which does not have mandated E10.

Results: In 2004 (the latest year for which data is available) Minnesota drivers drove 56.570 billion miles using 2.744 billion gallons of fuel. Their average fuel mileage was 20.62 mpg.

In that same year, Wisconsin drivers drove 60.399 billion miles using 2.592 billion gallons of fuel for an average of 23.30 mpg.

Minnesota drivers actually drove less than their cheesehead neighbors, but used more fuel to do it. Something caused Minnesota drivers to get almost 12% worse fuel mileage than their neighbors to the east. What do you think that could have that been?

Both states have almost identical topography, climate, demographics, and about the same mix of urban/rural driving. (In fact, Wisconsin has a slightly higher ratio of urban to rural miles driven.) The two states are about as close to being twins as any two states could be. (Not counting the Vikings/Packers difference of course.) Yet mileage in Minnesota is worse and their drivers burn and have to buy more fuel than their neighbors across the Saint Croix and Mississippi Rivers.

The only obvious difference that jumps out is that Minnesota forces its drivers to burn a blend of ethanol and gasoline with its known lower energy density.

The facts are pretty clear: The results of this huge sample size – the entire State of Minnesota – are much closer to my experience than to yours.


Gary Dikkers
Oh, and please hurry up and finish reading The Omnivore's Dilemma especially the section about the corn industry -- how much water and other natural resources are used to grow corn and the effect that has on the environment.

Did you know the corn ethanol you burn is only possible because of natural gas -- the natural gas used to make all the synthetic nitrogen fertilizers the corn industry uses each year because they've mined all the natural nutrients from that deep black soil in Iowa?

Whenever I hear someone describe corn ethanol as a “renewable” fuel, I have to laugh because they obviously have no clue how dependent that corn ethanol is on natural gas which is, of course, an unrenewable fuel.
You'll notice I based my conclusions on source data and a clear methodology. If the data and methodology you're using are available, I'd encourage you to publish them (though not here -- find your own space). If they're not available, I don't know why you'd expect me to trust your summary, as you're clearly biased toward specific conclusions.
Scott said, "If they're not available, I don't know why you'd expect me to trust your summary, as you're clearly biased toward specific conclusions."


My only bias is towards the truth. Are you doubting official statistics from the U.S. Department of Transportation (USDOT)?

It's right here: FHWA USDOT 2004 Statistics

Average mileage in Minnesota with mandated E10 -- 20.62 mpg

Average mileage in Wisconsin without mandated E10 -- 23.30 mpg

I understand why the ethanol industry doesn't want to hear that and would probably like to suppress that data. I also understand why the Governor and legislature of Minnesota would rather not publicize that, but unless there are some statisticans and mid-level bureaucrats at USDOT fudging the data, I have no reason to doubt its validity.


Gary Dikkers
I don't doubt USDOT data. I doubt your reading of the data, because I don't believe your bias is towards the truth. From the report you pointed to:

Users of these data must be careful to avoid "double counting" of the statistical data that could result from the effect of intergovernmental relationships. This is particularly so with reference to tables in the finance and mileage sections, because of the overlapping of Federal-aid activities with the State and local highway activities, and the effects of grant-in-aid programs.

I think it's clear from this that the numbers you're pulling out of this data are unreliable measures of fuel efficiency. And how could they possibly be reliable for comparison? The fuel in your vehicle doesn't magically change to ethanol when you cross the state border.

You're free to state these numbers as if they're a clear indication that ethanol contains no energy, and you're free to make vague inuendo about some big ethanol conspiracy, but you're not free to do that here. This site is not your personal soap box. Please take your agenda somewhere else.

It's your website and ultimately you make the final decision on what appears, but I would point out it's not sporting to make an ad hominem attack and not let the subject of that attack respond.

[additional text removed by Scott]
Gary, you're right, it's not sporting. This is not a sport and I'm not making an argument about ethanol fuel efficiency; I'm just reporting what I found in my own experience, and encouraging everyone else to do their own testing. And I'm not saying I don't trust you to support some point. I'm saying it because I really don't trust you. Anyone else is free to trust you if they want, but nothing you're saying is making me trust you more and I'm not providing you (nor anyone else) a forum to publish talking points here, so take it somewhere else.
Gary, problem with your numbers... I'm from Wisconsin and there is a big difference between the two states. You can legally drive FASTER in Minnesota. Admittedly it is only 5 MPH difference but in many vehicles that is significant. Here's an example. Years ago we drove to Montana in an 89 Escort. In Wisconsin and Minnesota @ 55 MPH I got 40 MPG. In Minnesota and North Dakota I got 34 MPG @ 70-75. In Montana there wasn't a daytime limit we got 28 MPG @ about 80 MPH.

In addition a large percentage of the gas stations in Wisconsin are E10 too. Your numbers aren't a valid comparison.
Kerry said, In addition a large percentage of the gas stations in Wisconsin are E10 too. Your numbers aren't a valid comparison.


They're not my numbers. They come from the U.S. DOT website where they track fuel use and mileage driven in each of the states. They are official, and they are vaild for comparison.

The percentage of gas stations in Wisconsin that blend their fuel as E10 is about 40%.

There is NOT a big difference between Wisconsin and Minnesota. Discounting the "Packers v. Vikings" factor, the two states are as near being twins as two states can be. If I was comparing Wisconsin with Georgia, you might have a point, but Minnesota and Wisconsin have much in common -- similar demographics, similar weather, similar climate, similar topography, and a similar ratio of urban to rural miles driven.

The facts are there. Why be so reluctant to believe?

I decided to post this, (for what its worth), after reading the dialog above from Gary who seems to be of the 'if you're for, I'm again' it' crowd, no matter what the subject.

As the manager, (for the past 10 years), of a 130 vehicle fleet, of which over half were older alternatively fueled or flex fuel conversions that enabled them to burn propane/gasoline; or LNG (Liquified Natural Gas); or CNG (Compressed Natural Gas), I decided to update my experience and test the most current FFV Conversion senarios on the market by converting my personal '98 Ford F-150 XLT 2x4, 1/2 ton pickup to a modern FFV (Flex Fuel Vehicle) that is alternatively capable of burning a full tank of E-85 Ethanol; or a full tank of 86 octane unleaded gas; or, any mixture of the two [without having to flip a selector switch].

I decided to 'walk the walk', (so to speak), by using my own one-owner, 95,xxx mile, vehicle that I know, without a doubt, has been well treated and maintanined. Thus, many of the questions about how it 'might' react to a steady diet of 85% Ethanol/15% Unleaded Gasoline were answered up front.

After 4,000 miles, and counting, I have NOT been disappointed. The results have been surprisingly positive and I have numerous Dyno runs and two Emissions tests, (paid for out of my own pocket), to prove it.

After considering the results, I am convinenced that they can be copied in 'almost' every, well maintanined, gasoline powered vehicle on the roads of America today. Such FFV conversions that would enable 'almost all' 1990 and newer vehicles to burn E-85 could measurably reduce many of the adverse emissions we're pouring into our air with every mile we drive.

The Dyno runs on my 4.2L V-6 engine at 5,000' above sea level have recorded a 12+ Horsepower & 5.5 ft-lb Torque increase but, more importantly, the Exhaust Emissions recorded by the City of Albuquerque, New Mexico's Main Emissions Testing Facility show are the real benefit of the FFV Conversion of an older vehicle.

Caviat; Poorly maintained or misused vehicles will likely never qualify for clean emissions. (You just can't make a silk purse out of a sows ear.)

The results of two (2) separate City of Albuquerque emissions tests are as follows:
HC (Hydrocarbons) = 13-17ppm (where 100 is max. allowable);
CO (Carbon Monoxide) = 0.00-0.01% (Where 1.00% is max. allowable);
CO2 (Carbon Dioxide) = 15.3% (where 16.0% is optimum and 14.7 is ideal);
O2 (Oxygen) = 0.32% (where the lowest possible is desireable);
NOx (Nitrogen Oxides) = not measured since they do not have the equip. to do so HOWEVER, numerous 'permeation' tests conducted by the Calif. Air Quality folks have shown that there are virtually NO Nitrogen Oxides emmitted when burning E-85 in an engine designed to burn gasoline. (Diesel engines are another issuse altogether.)

As for fuel usage of my FFV conversion buring 100% E-85 over the 4,000 miles, (at operating altitudes of 5,000'-7,800' above sea level), I have recorded usage between 13.5 mpg at 78mph, (on the interstate), to 17.8 mpg on the same road at 60 mph. On one 420 mile trip, (210 miles non stop each way), with the cruise control set at 60 mph, the average E-85 usage was 16.5mpg with a tail wind and 15.5mpg on the return trip with a head wind.

Scott, my findings seem to coincide closely with your findings and I fully agree with you that fuel usage is as much a matter of where you drive and, more importantly, HOW you operate your vehicle. Jack rabbit starts from a red light will cost you no matter what you've filled your tank with.

Yet, the 'Anti Ethanol' crowd have readily dismissed my positive emissions test results with a 'shrug' and then, without missing a beat, they will immediately counter with the old '90% negative energy balance argument' that is based on one study dating back to the early 1990's. (If you can't convince them confuse them !)

Conveniently, they always seem to completely ignore, (and not EVER mention), any of the 7 or 8 much more recent studies that totally refute the earlier negative study with results that show a positive Ethanol Production energy balance of between 1.3% & 1.6%. (BUT, that's a totally separate discussion.)

If anyone is interested, and if you're aminable, Scott, I'll be glad to post the hardcopies of my Dyno Run graphs and the City of Albuquerque Emmissions Test results. If you prefer, I will send them to you so you can study them before posting them.

Respectfully submitted,

George C. Koppmann
Santa Fe, New Mexico

'98 Ford F-150 XLT, 2x4, 5 Spd Auto;
4.2L V-6 SFI engine w/ K & N Air Filter
in an opened OEM Air Filter Housing;
FFV E-85 (Ethanol) Conversion using
a Full Flex Gold Kit [];
a 3" MagnaFlow 'After Cat' Exhaust Pipe,
SS Muffler & 3" Tail Pipe; Auburn 4:11
Limited Slip Differential.
Hi, I just wanted to jump in and say that it partially depends on what the engine manufacturer was intending you to run in your engine. I have a 1997 Niisan Sentra, and it specifically states in the owners manual that ethanol blends are not recommended. I live in the Madison area of Wisconsin, and I have a hard time finding 100% gas. I happened upon one accidentally a good way out of town, and my gas mileage improved dramatically (up almost 10MPG). So it's not just the gas, it's how your particular car was made.

That's my $0.02

It's like I told my wife: Some people will argue with you about the most trival matters until the day they die just because they think they are right and you are wrong.
Ethanol wins! End of story, wait till this cellulosic ethanol comes onto the market, its gonna be much better than the corn ethanol we currently have.
I agree with Clayton.

Also, I'd like to point out that 'efficient' is a relative term. I am assuming your parameters are cost and energy production, but I would like to make sure...
Hi. Here is my impartial blog of my experience with E85 here in Denver in my 2002 Chevy 'Great White' Tahoe FFV.

Could George C. Koppmann of
Santa Fe, New Mexico contact me? I'd like to see the emissions and Dyno numbers.

Be number 19:

knows half of 8 is