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VTT study finds no significant difference in car fuel consumption between E10 and E5

A study conducted by VTT Technical Research Center of Finland indicates that there is practically no difference between commercial gasoline grades 95E10 and 98E5 sold in Finland as regards fuel consumption in normal driving. The finding is based on driving tests conducted by VTT using six used cars of different make under laboratory conditions.

VTT noted that it has been frequently claimed in public that fuel consumption is significantly higher with 95E10 than with its predecessor 95E or the 98E5 currently on the market. The suspected higher consumption has deterred drivers of cars whose manufacturers recommend E10 from actually using it.

The point of this study was to highlight how fuel consumption should actually be measured to give comparable results. Measuring fuel consumption very accurately is not as simple as it seems, because other factors affect consumption besides the fuel itself. In laboratory conditions, we can eliminate these other factors.

—Juhani Laurikko, a Principal Scientist at VTT

The VTT measurements show that the cars tested used an average of 10.30 liters of 95E10 per 100 km, as opposed to 10.23 liters of 98E5 per 100 km. The difference was 0.07 in favor of 98E5 on average, meaning that using 95E10 gasoline, which has a higher ethanol content, increases consumption by 0.7%. Normalizing measurement results of each individual test run with observed slight scatter in actual total work done over the driving cycle yields to somewhat higher overall difference, 1.0%.

Summary of test results. Click to enlarge.

An estimation of calorific values based on approximate fuel composition came out at 1.1% in favour of E5, which is highly consistent with the aforementioned 1.0% difference in consumption. Fuel consumption depends mainly on the calorific value of the fuel, i.e. its energy content per unit of volume or mass.

VTT obtained all the fuel used for the test runs at the same time from the Otaniemi Neste Oil service station in Espoo. So as to ensure that ethanol contents was in accordance with the specifications, the ethanol contents of both fuel batches was determined by the Finnish Customs Laboratory. The results showed 4.7% for the E5-grade and 9.4% for the E10 grade.

VTT performed the comparison test under controlled laboratory conditions, because of practical and almost unsurmountable difficulties in measuring a car’s fuel consumption accurately and repeatability in normal driving. Therefore, the public claims concerning differences in fuel consumption may be due to any number of other factors besides the type of fuel used.

The study involved six gasoline-driven cars loaned by VTT employees. The cars were of model years between 1999 and 2010 and, according to their manufacturers’ recommendations, compatible with E10-fuel. The cars were checked to ensure they were free of any faults or malfunctions that could have influenced the test results.

VTT measured fuel consumption using the simplest and most reliable method: measuring the weight of fuel consumed. As the density of the fuel grades was known, establishing the volume of fuel consumed was a simple matter.

The driving program used for the test drives was the FTP72 programme, which features more aggressive accelerations and a high average speed than corresponding EU cycle. Two drivers were used for the tests, both of them experienced and qualified for conducting accredited exhaust emission tests. Each car was driven by the same driver in all tests. Two tests were conducted on consecutive days for each petrol grade. The running order of the fuels was random.

The study is a part of the five-year TransEco research program launched at the initiative of VTT to make road traffic energy use more efficient, develop emissions-reducing technologies and commercialize the results of the development work.



I would expect about a 3% difference. It depends on the engine and how it works with E10 versus E5. A lot of people posting on news sites say that E85 gets so much worse mileage and it does not cost much less. They do not take into account that it is domestic and reduces oil imports. I guess self interest beats helping.


I think this article is a bit of a cheat; it starts by saying the study found no significant difference between E5 and E10 and THEN goes on to say E5 is better by an average of .7%. Call me cheap if you want but when I'm the one filling the tank that .7% is significant to me.

But the real cheat is that the title baits us with "E5 and E10" but the fuels tested were 95E10 and 98E5.

I assume the 95 and 98 numbers are for the octane of the fuel.


On a cost per BTU basis it is about equivalent. If the oxygen sensors and engine computer do their jobs there should be no problem. The problem is we use corn grain to make ethanol instead of cellulose. The problem is we have 0.1% E85 pumps for 3% of the FFV vehicles on the road. Once we make ethanol from cellulose, get 30 times the number of E85 pumps and pass the Open Fuel Standard, then we can to some good. The GOP will never allow that, so we remain stalled in a declining situation over and over again.


Ethanol Org. claimed that, with three different cars, the average was:

1. E-10 gets 1.48% less miles per gallon
2. E-20 gets 2.19% less miles per gallon
3. E-30 gets 5.34% less miles per gallon

Does this mean that E-85 would get about 12% less miles per gallon?

It seems that large V-6 get better results than small 4-cyls.


People expect to get about 70% of the mileage on E85, but they are reporting 80-85% of the mileage, depending on car location, temperature and other factors.


SJC...it is very possible that Ethanol Corp overstated the miles per gallon for for various ethanol blend.


Gentlemen, regardless of mileage, expanding the fleet of domestic (non-fossil) fueled vehicles falls within the platform of the GOP. The wise will make use of this portal to legislate more FFVs in the light duty fleet AND pass the Open Fuel Standard.

The fastest path to non-fossil energy is Energy Independence. Grok this. Support this. And change WILL come.

Tom Watson

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