By 'more efficient' I mean burning a gallon of gasoline might use 35% of the btus in a gallon to move the car and waste 65% as heat in exhaust and friction.
An E85 vehicle might use 37% of the available btu and waste 63%. Because of the cleaner burning, added oxygen, and more even flash point.
If you run through all the math, a gallon of E85 has less BTU so it gets less mpg, but that 2% better efficiency means 50,000 btu of ethanol will get you farther than 50,000 but of gasoline. The ethanol is more efficient, tho starts out with less btu.
Actually taking everything into consideration, ethanol returns 1.3 units of energy for every 1 unit of energy used in making it, in a full on energy audit of the process from seed to tank. This is not really all that earth shakingly great, but none the less it is a net energy increase. It will be nice of someday we get something with a better conversion rate, but today 1.3 is better than doing nothing......
As well ethanol generally uses lower forms of energy to create a liquid fuel energy, and that conversion has a value too, it is enhancing the value of a non-mobile heating fuel like natural gas into a higher btu transportation fuel. Value added.
And we are running ethanol in engines designed for gasoline. Of course that is not ideal. If we could design the engine to run on E85 from the get go as Brazil does, ethanol would look much better than it does now.
But I understand, folks from oil states especially are fed a lot of rather partisan info. And as a farmer that grows corn, it doesn't pay for me to get on a soap box too much.
Ethanol adds a little bit to our fuel supply, it allows use of lower octane gasolines which lets is get more gallons of fuel per barrel of crude, it changes the pollution to slightly better air quality. A lot of positives to ethanol.
It isn't going to change the world long term, it isn't any sort of total solution to our energy needs. But it is a step to change, and a step in the right direction.
Paul