The E85 Solution

Because we must burn more E85 than gasoline to make the same amount of heat in the combustion chamber, E85 is currently not the dashing hero as an alternative daily-driver fuel. While there is a 27 percent reduction in heat, ethanol's strong octane rating allows the use of a higher static compression ratio to take advantage of that resistance to detonation. This means if you were to run E85 in an 11:1 or 12:1 compression engine, E85's higher octane would prevent detonation, which would allow you to run this higher compression ratio and take more advantage of the reduced Btu heat output by squeezing the existing air and fuel a little harder to make more power. The kicker is that right now, E85 is priced only about 30 to 50 cents a gallon cheaper than gasoline. During research for this story, we priced E85 at a gas station in Ames, Iowa, at $2.60 a gallon, which is significantly below the price of 93-octane premium at $3.05 per gallon and far less expensive than $5 to $6 per gallon for 100-octane unleaded race gasoline. Higher-octane race gas is even more expensive. With reduced mileage, E85 only becomes economically attractive from a mileage standpoint when E85 is significantly cheaper per gallon. Also keep in mind that the government is currently subsidizing ethanol at around 50 cents per gallon. If ethanol use increases dramatically in the next few years, expect the government to yank that subsidy in order to cash in. The other big problem with E85 is availability. Because corn is the most popular base stock for ethanol, the Corn Belt states of Iowa, Nebraska, Missouri, and Minnesota are the places where E85 is most prevalent. There are only 15 states that do not offer E85, concentrated mainly in the upper northeast United States along with Alaska, Hawaii, Arkansas, Louisiana, and Alabama. The entire state of California has only one bulk outlet, in San Diego, where E85 can be purchased by the public. But take heart, this situation is rapidly changing, and within a year or two, the E85 landscape could change. But for those of you in the Midwest states, you have no excuse for not checking this stuff out.

The Octane Game
The definition of octane is rather confusing. It's also called the antiknock index (AKI) and refers to a fuel's ability to suppress detonation. The higher the AKI number, the better the fuel's ability to prevent knock. Octane by itself does not add power to your engine. However, a low-octane fuel will not allow a performance engine to achieve its optimal ignition timing and power due to detonation. Detonation is defined as uncontrolled combustion where high cylinder pressure can auto-ignite end gases in the cylinder that tend to increase the opportunity for this process to be self-sustaining. This creates a massive pressure spike that literally rattles the pistons in their cylinders and kills power. Using a higher-octane fuel allows an engine to take advantage of an ideal timing curve without causing detonation. Once that timing has been achieved, there is no advantage to using higher-octane fuel.

You may have seen octane stickers on gas pumps that list the AKI using the equation R + M / 2 = Octane. The R stands for research octane number (RON) while M represents motor octane number (MON). RON is always much higher than MON, which is why the AKI uses an average of the two numbers to best represent the AKI for street-driven engines. The accompanying chart lists both RON and MON for ethanol and methanol plus a couple of popular race gasolines so you can get an idea of how ethanol and E85 compare.

Straight ethanol has an AKI rating of 113-115. E85 is generally rated at between 100 and 105, depending upon the manufacturer. The E85 we tested, supplied by American Ethanol out of Chicago, is rated at 105. E85 is most often blended with 87-octane gasoline, since it is the least expensive. Another advantage to ethanol is that the greater volume of fuel required also tends to reduce inlet air temperatures, where evaporating fuel pulls heat out of the incoming air temperature.