Ethanol and Mileage- More information

I heard that a reader has questioned whether my April 15 post regarding ethanol was correct in suggesting that E-85 ethanol blends provided significantly lower mileage than regular unleaded gasoline. The reader thought that this differential was closer to three percent, which is not much. I did some further checking, and I identified two sources that speak to this issue.

First, the Illinois Corn Growers (whom you could expect to take a favorable view about ethanol) state as follows on their website:

How will mileage and fuel economy be effected[sic]?
A gallon of E-85 ethanol fuel contains about 2/3 the energy of a gallon of gasoline. This means the E-85 vehicles should get about 2/3 the fuel mileage of the gasoline versions of these vehicles. However, the E-85 vehicles in the Illinois fleet are getting 5-10% above what was expected or 18-20 miles per gallon. Repairs and reliability of the E-85 Luminas have been slightly better than their gasoline counterparts.

Source: The Illinois Corn Growers Association
http://www.ilcorn.org/Ethanol/85__Ethanol/85__ethanol.html

Another study funded by the American Coalition for Ethanol focused on the mileage of 10% ethanol blend, which is commonly used in Iowa. The study reported that the 10% blend has 3% fewer BTUs than the same gallon of gasoline. However, that there is some indication that mileage does not always precisely track BTU content. For example, their tests showed much closer mileage spreads.
http://www.ethanol.org/documents/ACEFuelEconomyStudy.pdf

Thus, it appears that the 3 percent differential is for 10% Ethanol, not the E-85 mentioned in my prior post (which is 85 percent ethanol). The 10 percent blend regularly sells in Iowa for less than regular unleaded, and it requires no engine modifications. (Older vehicles might experience problems with fuel filters, though, if you have not burned ethanol before.) At an estimated $2.80 for ethanol blend and 2.85 for regular unleaded, if the mileage differential is three percent you probably would be ahead paying for the regular unleaded. You would need a much bigger discount for the E-85 fuel, though, as the increasing ethanol content means much less energy and, to some degree, lower mileage.

I hope this information helps. I note that this information comes from ethanol-friendly organizations, so if you think there is a conspiracy, you'll have to find another test to satisfy yourself. Or what the heck - why not do your own? You'll find it may not even be so difficult being "green". From my own experience, the mileage difference is small - but my driving habits vary depending on what music I play and how many semis are bearing down on my tail end as I try to accelerate gently. Sometimes fuel economy is not the top priorty, no?

Query whether we will see a larger discount for ethanol as petroleum prices rise relative to ethanol (and corn). The 5 cent discount that appeared when gas was $1 plus was closer to an even exchange assuming a 3 percent mileage disadvantage.

EAM