Driving

The energy of ethanol relative to gasoline
 A.  76,000  = BTU of energy in a gallon of ethanol
 B.  116,090 = BTU of energy in a gallon of gasoline
 C.  .655 = 2/3 = GGE of energy in a gallon of ethanol.  A / B. (GGE =energy in a gal. of gas)
 D.  1.53 = Gallons of ethanol with the energy of 1 gallon of gasoline.  D = B / A.

The basic story on ethanol mileage and cost

Some Ethanol proponents claim it doesn't hurt their mileage, but this goes against physics, and you will not find the ethanol lobby making such fraudulent claims--they could be sued. But just to be sure, zFacts analyzed all of EPA's ethanol mileage tests for one year and, big surprise, ethanol gave exactly 2/3 the mileage of gasoline.
Now there is one possible loophole and it is used by a Swedish sports car, the SABA 9-5 Bio-power. Here's the trick. Higher compression ratios make engines more efficient, and because of its high octane, ethanol can take a higher compression ratio. The Bio-power is turbo charged and when it uses E85 it switches to a higher compression ratio. It still gets fewer mpg on ethanol, but it does a little better. Unfortunately it's very expensive. An easier approach is to use diesel, which also gives you a high compression ratio and mileage as good as a hybrid at less cost. That's why all big trucks are diesel.
The USDA tells us that ethanol cost 57¢ more per gallon on average over the last 25 years (and it still does). Put that together with the fact that it takes 1.53 gallons to equal a gallon of gasoline.
 
 

23% extra fuel cost of using E85 with 2006 models
The EPA has measured the gas mileage of 2006 flexible fuel models. For the 31 models they tested the average reduction is 26% fewer miles per gallon. For example a car that gets 30 mpg on regular would typically get 22.2 mpg with E85. This is exactly what is predicted from the fact that E85 has less energy per gallon than gasoline.

For these calculations, the EPA assumes that E85 costs $2.00 and regular $2.20/gallon. Obviously they are on the low side, especially for ethanol, but this proportion is similar to what DOE predict for the next few years. The loss in mileage more than makes up for the cost savings, and on average the EPA predicts driving on E85 will cost 23% more than driving on regular.

 
 

Here's a letter from someone using only E85.
He's getting slightly worse mileage than predicted by ethanol's low energy: 2/3 the energy of gasoline. But Sam has been fooled by the deceptive (but true) claim that Ethanol has high octane and thinks he should actually get better mileage.

Sir;

I have a 2003 Chevrolet Suburban. The ONLY fuel I have used on this vehicle is the Ethanol 85, and I am not happy.
1.)   I have seen that in other states the price of Ethanol is LOWER than regular gas.  I go to the gas station in Annapolis, Maryland on West Street.  The price for this fuel is $1.95 per gallon.  The regular gas price is $1.43 per gallon in my area.
2.)  This fuel is rated at 100 Octane and SHOULD result in better fuel mileage.  My vehicle is rated from 16-22 MPG.  Since I have gotten this vehicle and using this fuel I cannot get ANY better than 13.2 MPG.
I believe in this program and want to continue to support it. I am a retired police officer and not made of money. My friends laugh at me and call me a fool.  They say my intentions are great, but NOT at that cost.

SAM WALTERS
Annapolis, MD.

This letter was posted by National Ethanol Vehicle Coalition. They answered, but did not tell him why he was getting low mileage—they don't want people to know.

This is what the Iowa Dept. of Agriculture tells us:

"E85 is priced to be competitive with 87-octane gasoline. In Iowa, prices typically range about 8-10 cents more than regular unleaded."

Even at the same price, E85 would be 41% more expensive than regular gasoline.

 
 

Ethanol has only about 2/3 the energy of gasoline

The lower heating value (LHV) of conventional gasoline = 115,500 Btu/gallon
The lower heating value (LHV) of ethanol = 76,000 Btu/gallon

Hence it takes 115.5/76 = 1.52 gallons of Ethanol to replace the energy in one gallon of gasoline.

Every fuel has two energy values, sometimes called lower and high heating values. The lower value is the energy you can get without condensing the water out of the exhaust. "Condensing furnaces" for your home do just that and can almost recover the higher heating value. Cars cannot use steam in their exhaust; it just goes out the tailpipe.

For cars, and all internal combustion engines, the lower heating value is the relevant value, yet DOE almost always publishes the higher heating value.

 
 

How much should you pay for E10 and E85?
If regular gas is $3.00/gallon you should pay
      $2.90 / gallon for E10 (10% ethanol).
      $2.13 / gallon for E85 (85% ethanol).
If regular gas is $2.00/gallon you should pay
      $1.93 / gallon for E10 (10% ethanol).
      $1.42 / gallon for E85 (85% ethanol).
Then you will be paying the same amount per mile driven.

The formula is this: For EX, where X is the percent ethanol

     Ethanol price should = Gasoline price times (100 – X + X/1.52)/100

Notice that 100 – X is the percent of gas and X/1.52 is the percent of ethanol adjusted down by about 2/3 because it has less energy.

 
 

New Recipe For Gasoline [Ehanol] Helped Drive Up the Price
NY Times, May 6, 2006, By MATTHEW L. WALD

WASHINGTON, May 5 — Nine months after Congress passed major energy legislation, one provision affecting gasoline formulas is helping to drive the price of gas up much faster than the rising price of crude oil.

Ethanol is pricey and energy-poor. Its price is up by about $1.30 a gallon in the last year, in part because of heavy demand for something to replace MTBE. But ethanol has only about two-thirds as much energy. 

And because the new gasoline recipe contains less energy, mileage per gallon is declining. 

On Friday, ... the Energy Policy Act of 2005 ended the requirement that gasoline sold in areas prone to air pollution include an "oxygenate." ... Refiners over most of the country's big gasoline markets, anticipating the rule, have already dropped the chemical MTBE.

The refiners were not explicitly required to drop MTBE, but virtually all have done so because it has polluted groundwater and exposed them to liability suits. ... But now refiners must replace that ingredient. And they need a substitute that is also high octane, as MTBE is. Refiners have turned in part to ethanol, which is also an oxygenate but not a pollution worry.

Ethanol costs more than gasoline, and shipping it from the Midwest, is cumbersome and expensive, because it has to go by barge, railroad tank car or tanker truck, rather than pipeline.

West Texas Intermediate, the American benchmark oil, was up only about 39 cents a gallon last month compared with April 2005, while the wholesale price of gasoline rose about 64 cents over the same period. ... Experts at the Energy Department, the refiners' trade association and elsewhere agree that the changeover from MTBE was a factor, although they differ about the amount. ...

The oxygenate requirement has been obsolete for years. It was intended to make the fuel mix leaner, reducing air pollution. But that works only on older cars, with carburetors, not in modern vehicles with oxygen sensors and fuel injectors.

NY Times

 

Does the SAAB 9-5 beat the ethanol mileage problem?

Autobog gives these values.
Gas 25.7mpg@30mph, 22.9mpg@50mph, 16.0mpg@70mph
E85 17.4mpg@30mph, 15.8mpg@50mph, 11.4mpg@70mph.
That averages to a 31% reduction in mileage, which is more than other cars.