[KarlInOhio]

Brad Cloven: "Two publications, Consumer Reports and CARandDRIVER in recent road tests or on an oval track, in 2006 trials found that E85 (gasoline mixed with 85 percent alcohol) has approximately 30 percent less mileage as compared to 87 octane gasoline."

Wonder Warthog: Which basically says that ethanol is a MORE EFFICIENT fuel than gasoline, based on the BTU/gallon ratios.

Huh? If you mix 0.85 gallons of ethanol at 75,670 BTUs per gallon and 0.15 gallons of gasoline at 115,400 BTUs per gallon, you get E85 at 81629.5 BTUs / gallon (assuming that does equal 1 gallon which isn't true for some mixtures). That 81629.5 is 70.7% of the gasoline energy density, thus I would expect it to get 29.3% less mileage than gasoline. That is almost identical to the 30% reduction Car and Driver found. I think you messed up by assuming that E85 had the same energy density as ethanol.

[Wonder Warthog]

"I think you messed up by assuming that E85 had the same energy density as ethanol."

Of all the folks who responded, you're the only one with two braincells to rub together---you're right. But what this STILL says is that on a BTU/BTU comparison, ethanol is NO WORSE than gasoline.

[supercat]

I think you messed up by assuming that E85 had the same energy density as ethanol.

The miles/BTU comparison does not have to do with miles per gallon, nor miles per dollar, but is interesting in its own right. Most of the energy that goes into an internal combustion engine goes out the tailpipe. Less than half of it goes into pushing a car down the road.

For some reason, cars running on ethanol are able to use a larger portion of the energy in their fuel into pushing the vehicle down the road than cars running on gasoline. While this fact may not be useful in and of itself, it would suggest that it might be useful to focus some research on ascertaining the reasons for the differences and using them to improve the efficiency of gasoline-powered cars.