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Study Finds Certain Ethanol Blends Can Provide Better Fuel Economy Than Gasoline

Highway fuel economy improvement, E20 and E30 vs. Tier 2 gasoline. Click to enlarge.

Research findings released today indicate that mid-range ethanol blends—fuel mixtures with more ethanol than 10% (E10) but less than 85% (E85)—can in some cases provide better fuel economy than regular unleaded gasoline, even in standard, non-flex-fuel vehicles. The new study, co-sponsored by the US Department of Energy and the American Coalition for Ethanol (ACE), also found that mid-range ethanol blends reduce harmful tailpipe emissions.

Previous assumptions held that ethanol’s lower energy content directly correlates with lower fuel economy for drivers. Those assumptions were found to be incorrect. Instead, the new research suggests that there is an optimal blend level of ethanol and gasoline—most likely E20 or E30—at which cars will get better mileage than predicted based strictly on the fuel’s per-gallon Btu content. The optimal blend varies with the vehicle, according to the findings.

The University of North Dakota Energy & Environmental Research Center (EERC) and the Minnesota Center for Automotive Research (MnCAR) conducted the research using four 2007 model vehicles: a Toyota Camry, a Ford Fusion and two Chevrolet Impalas, one flex-fuel and one non-flex-fuel.

Researchers used the EPA Highway Fuel Economy Test (HWFET) to examine a range of ethanol-gasoline blends from straight Tier 2 gasoline up to 85 percent ethanol. All of the vehicles got better mileage with ethanol blends than the ethanol’s energy content would predict, and three out of four actually traveled farther on a mid-level ethanol blend than on unleaded gasoline.

In addition to the favorable fuel economy findings, the research provides strong evidence that standard, non-flex-fuel vehicles can operate on ethanol blends beyond E10. The three non-flex-fuel vehicles tested operated on levels as high as E65 before any engine fault codes were displayed. Emissions results for the ethanol blends were favorable for nitrogen oxides, carbon monoxide and non-methane organic gases, showing an especially significant reduction in CO2 emissions for each vehicle’s optimal ethanol blend (E20 for the flex-fuel Chevy, E30 for the Toyota and Ford, E40 for the non-flex Chevy).

Ethanol’s energy content was not found to be a direct predictor of fuel economy. All four vehicles tested exhibited better fuel economy with the ethanol blends than the Btu-value estimates predicted.

E20 and E30 ethanol blends outperformed unleaded gasoline in fuel economy tests for certain autos. Contrary to Btu-based estimates of fuel economy for ethanol blends, three of the four vehicles tested achieved their highest fuel efficiency not on gasoline, but on an ethanol blend. Mid-level blends of ethanol E20 (20% ethanol, 80% gasoline) and E30 (30% ethanol, 70% gasoline) offered the best fuel economy in these tests.

  • E30 offered better fuel economy than gasoline (a 1% increase) in both the Toyota and the Ford.

  • E20 offered better fuel economy than gasoline (a 15% increase) in the flex-fuel Chevrolet.

  • The non-flex-fuel Chevrolet more closely followed the Btu-calculated trend for fuel economy, but did experience a significant improvement over the trend line with E40 (40% ethanol, 60% gasoline), indicating that this may be the optimal ethanol blend level for this vehicle.

The standard, non-flex-fuel vehicles operated well on ethanol blends beyond 10%. The Ford Fusion operated on E45, the Toyota on E65, and the non-flex-fuel Chevy on E55. No engine fault codes were displayed until these levels were surpassed.




my brother has been saying for years that he puts e85 into his work van and pickup (neither of which are flexfuel) and that he gets better performance and fuel economy. i used to just laugh in his face but if this industry-sponsored report is true (i am skeptical, but intrigued) i just might owe him an apology!

Harvey D

A friend who worked for one of the large refinery says that this is not surprising because gasoline is blended to maximize consumption in most ICE vehicle, like nicotine in cigarettes.

Consumption reducing blends would not be very popular with refineries and retailers. It is simply not in their best interest.


All I remember is that a small amount of ethanol will raise octane. That permits raising the compression - which obviously is not up to the driver - and/or optimizing ignition timing.

I never knew much about ignition and have no idea if cars can now automatically change the ignition curve based upon fuel. They do sense and prevent knock.

And variable valve timing might also be a factor. But most engines still don't do that.



From what I have personally seen it is more typical of high performance engines which normally require high octane gas or use forced induction to have knock sensors to adjust ignition timing.

I wonder if ethanol's ability to evaporate (more readily than gasoline) and pull heat out of the combustion chamber has any impact here? Greater difference in temperature usually gives a higher thermal efficiency (between initial state and combustion with the initial state being just prior to combustion).

Rafael Seidl

@ Harvey D -

refineries can tweak fuel formulations, e.g. using additives. They also strive to deliver a product with density and octane rating near the lower end of the standard required for a given fuel grade, simply because that is cheaper to produce and yields more fuel per barrel of oil. Much depends on the composition of the crude, though - light, sweet grades command the highest prices.

Ethanol does feature lower energy density by weight and volume than gasoline, but the octane number is high. Engines featuring a relatively high compression ratio and automatic knock detection can therefore advance the ignition when fed an ethanol blend. GDI engines should fare even better because ethanol's high latent heat cools down the fresh charge more effectively. Beyond a certain blend level, the blend's aggregate evaporation characteristics and that energy density will reduce volumetric fuel economy again.

E85 was chosen primarily because that's how high you can go with relatively cheap upgrades to the fuel system. It also appealed to midwestern politicos looking to curry favor with farm interests at a time when demand for corn ethanol was low, especially since blends are typically not permitted in distribution pipelines for fear of corrosion. Ethanol is highly hygroscopic.

The good news is that IFF cellulosic ethanol ever becomes available in large quantities at reasonable prices, a mid-range blend can deliver competitive operating range on a tank of fuel. However, engines and fuel systems would have to be optimized for and tested against a single standardized mid-range blend grade, e.g. E20. This would be preferable to E85 IFF the CAFE loophole were phased out as proposed in the House version of the Energy Bill.


Professor Mark Jacobsen in April 2007 stated that E85 has more health problems than gasoline. American Coalition for Ethanol(ACE) immediately jumped on him. Now ACE & the gov't says Ethanol has more MPG & better for your health? What a crock!

With billions of gallons worth of subsidies now pouring out of Washington D.C., both ACE & gov't have much to support that isn't supportable.

Tom Street

Isn't a flex fuel vehicle optimized for ethanol. Still doesn't mean ethanol is a good idea. The only statistic that seems potentially meaningful is the 1% increase, but then this was conducted by ACE. What an outrage that DOE would even work with them on this. Until I see an independent evaluation of this, I will give it zero credibility.


going back over fifteen years and prior to the introduction of unleaded petrol here in aus, E5 Mainly E10 started coming out at the same time the report in the Jounal Institute of Automotive Mechanical Engineers Australa New Zealand.
Described from memory, That the e blended fuels (both petrol and deisel)had substantially less emmisions for a statistically insignificant reduction in fuel economy.
Of particular interest was the reduction in particulate emissions from deisel engines.
This being due to a shattering effect on the unburnt particles.
It is those larger unburnt particles that were of interes at that time as they contributed large amounts of soot and haze.
The idea that these large droplet sizes were a poblem to health is somewhat outdated now as the smaller particle < xxnm seem to penetrate deeper to lung tissue.

Back to fuel economy. It stands to reason that if the fuel droplets are broken down more that the extra surface area will permit more complete combustion. This benifit would increase with he older (smokier vehicles. Hence improvents in fuel economy despite the lower Calorific value. So with higher pressure deisel injection, some of the benifits will be harder to realize in that "OLD MODEL".
That isnt to say that Ive seen the report yet on the new tests. Only to confirm that this summary is consistent with very credible reports from the pre greenhouse enhanced world.
Ive been a convert to those smaller E10 or 5 blends and any other bio products ever since and have never had any reason to suspect other than benificial outcomes, rather actively seek those fuels out. Despite the endless scaremongering by the vehicle manufacures and fuel co's..
Next step is to read the report.


So what they found can pretty much be described as
"It depends on the car model whether or not you won't get a mileage decrease. And no single blend fits the bill."


"Isn't a flex fuel vehicle optimized for ethanol."

Tom, not a single production example of an E85 capable vehicle is actually optimized for E85. It's mainly just bigger injectors and different materials used in the fuel systems that allow E85 to be used safely.

There have been some attempts to use turbocharging (see Saab's Biopower research) and/or variable compression to try to do just that though, but nothing has made it to production in the US. I believe Saab is testing a watered-down version of their Biopower concept in Sweden this year.


I'm surprised by how nonlinear the curves are with regard to percentage ethanol. It would seem that this would indicate a need to quickly determine a standard for what a mid-range will be... E20, E25, E30? Until such a standard is set, car companies won't be able to tweak their engines and controllers to assure the MPG peak is in harmony with what finally appears at the pumps... assuming we end up with anything between E10 and E85.

The mention of higher blends in non-flex vehicles seemed a bit off the mark. At least it is my understanding that just because the engine control system is still functioning at high blends doesn't mean the hoses and fuel delivery system are suitable for that much ethanol.


This is hardly new information. An engines efficiency is determined by how much heat the fuel absorbs when injected into the cylinder, how fast and how completely it burns, and how much it can be compressed before it burns. Ethanol outperforms gasoline in all of these areas. An engine optimized to run on ethanol will achieve at least 40% thermal efficiency. Engines optimized for gasoline will achieve about 25% thermal efficiency. Engines that can adjust the compression ratio can get better mileage on ethanol than on gasoline. Unfortunately most cars sold today cannot do that.

Since all vehicals sold in the US are optimized for gasoline (including FFV) most cars will experience a 10 to 15% loss in milage. Note the 30% most people assume based on the BTU content. People in the US and Brazil have found that most cars work fine with more than 30% ethanol in the fuel. People in South Dakota are are using E85 in modern none flex fuel vehicals without any engine or fuel system issues. The problem of ethanol damaging hoses and fuel system parts is mainly limited to cars made before 1970.

In the 1980's Brazil required all new vehicals run on 100% ethanol. Pollution levels dropped and plans for requiring emission controls on cars were delayed (all cars sold at that time did not have emission controls). In the 90's the ethanol requirement was dropped and most people switch to gasoline powered cars since gas cost less at the time. Pollution levels increased and emission controls are now required. So ethanol does burn cleaner than gasoline. So from an engineering point of view ethanol is better than gasoline.


"I believe Saab is testing a watered-down version of their Biopower concept in Sweden this year."

Saab's Biopower (E-85 turbocharged) cars are something like the #2 and #3 top-selling cars in Sweden, and have been for a while. It's safe to say at this point that they are not just "testing" the concept.


Agreed, and I would like to see them here!


Obviously this is a contentious issue. My feeling is that guzzling ethanol is worse than guzzling gasoline.
The ideal use of ethanol would be the MIT engine that meters the ethanol blend in realtime.
BTW E85-Flexfuel was a loophole written into law back in 1993 expressly for the benefit of Ford because it couldn't meet the CAFE standard.


According to automakers, ethanol is more corrosive. Using more than 10% ethanol is regular engine will lead to corrosion in the fuel system and engine and will compromise durability.

In flex-fuel vehicles, the fuel system and engine are specially designed to handle this corrosiveness.


I think it is important to note here (for those that are less scientific/engineering inclined) that there is a difference between "engine efficiency" and "Miles per gallon."

Efficiency is basically how much work the engine can achieve given a fixed amount of chemical potential. Or in simpler terms: how much energy you can get out of an engine for a fixed amount of fuel.

This sounds like MPGs... but efficiency is for a fixed amount of fuel in terms of energy content of the fuel. So when debating MPG's vs. Efficiency... the energy density of a fuel must be considered.

Ethanol definitely has the potential to be combusted at a higher efficiency (see earlier posts by our peers). BUT it has a LOWER energy density - there by lowering the MPGs.

This is analogous to saying which makes a louder bang: a barrel full of M80 fireworks or a barrel full of C4 explosives. It isn't fair to compare one to the other on a barrel basis.

When comparing fuels it is far better to use efficiency of the engine or to use gram CO2/km to account for the environmental footprint.

Mark A

Funny that this study was sponsored by ACE, the American Coalition for Ethanol. I wonder if favorable findings in this study would better their cause? Touting the use of ethanol should not be pushed until a viable wasy to produce it is found. Taking cropland used for food to grow fuel never will make any sense, but that is an argument for another time.

Using more than 10% ethanol in a non flex fuel vehicle will cause problems, not just the corrosiveness of the fuel, but the degrading of rubber/plastic seals and o'rings throughout the fuel system. Perhaps it would work fine for a month or so, but then performance and/or fuel economy numbers would start to degrade, and be hard to pinpoint why or where the problem is. May take a complete failure somewhere to find it.

Angelo made a funny concept about "SAAB is testing a watered down version......" I wonder if they fueled it up with ethanol, and let it sit for a week, to get the "watered down" effect??

richard schumacher

Readers who may be puzzled should note that "IFF" used above is not a typo; it's an abbreviation of "if and only if".


Let me clarify my, "watered down.." comment:

If memory serves, they are offering a 2.0 turbo in Sweden that produces about 150HP on gas and 185 on ethanol (not sure if that is E85 or E100). This is the same engine that has produced 175 or 210 in the US. It sounds like they could crank that boost up way higher when using ethanol if they wanted to.

Additionally, I think they showcased a 2.3 with DI at one point that was 260/315 or something like that. That better showcases what could be done.

My point is that if they want to highlight the benefits of optimizing an engine to run on high ethanol blends, they should use a very high specific output. Maybe a 1.6 that produces the same power as the 2.0/210 HP version, or a 2.0 in the 280 range.


Hey, that Ethanol Boost technique previously discussed here on would also come in handy here as an enabling technology for the variable delivery of car model-optimized fuel blends.

Michael Weng

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John L.

Posted by: Michael Weng | Dec 6, 2007 10:43:39 PM

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Ely Marc

This study is quite interesting. I'm exchanging email with the author. Brazil already has standardized on an E25 blend for ALL gasoline. I wonder if they already understood some of this. I'm working on a paper right at the moment; "Straight talk on ethanol". A lot of what you read in the popular press turns out to be wrong about ethanol. I see great promise in ethanol as a fuel.

fred schumacher

Most research universities get a major part of their research funding from private industry. If that makes the research worthless, then Patzek and Pimentel's ethanol studies would also have to be thrown out. Obviously more research is needed to see if UND's results can be replicated. Minnesota State University Mankato has also been working on high-ethanol percentage fuel evaluations and getting positive results.

Agriculture is not only about producing food. It has a long history of non-food fuel and fiber production. North Dakota State University became an international leader in paintings and coatings technology because of its research into industrial uses of linseed oil, a major product of North Dakota agriculture.

Ethanol can make the transition to smaller, more fuel efficient engines easier. Direct injection, HCCI, DiesOtto, supercharging, variable compression and valve timing would all work better with an ethanol blend. Smaller engines, less friction, lower weight form a symbiotic relationship to reduce fuel consumption. Reducing comsumption is the number one job.

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