[Herakles]

let me do a calculation that may not be exactly correct;

1 gallon of gas = $ 3.00

1 US gallons = 3.7854118 liters; so

3.7854118 liters = $3.00

At the liquor store, 1.5 liters of vodka (assume 100 proof potato ethanol) = $11.00

Replacing 15% of gas with ethanol;

.85(3.7854118 liters = $3.00) = 3.22 liters = $2.55

3.7854118 - 3.22 = .57

(.57/1.5)11.00 = $4.18

so gas with 15% vodka should cost $2.55 + $4.18 = $6.73

which is why we do not use vodka to fuel our cars; however this points out an important fact; if ethanol were the price of gas or less we would have been using it long ago, but it is nowhere near that so when it is added, the price of gas will go up.

[rahbert]

your 1.5 liters of 100 proof is only 50% ETOH by volume,
the rest is water.

[tortoise]

At the liquor store, 1.5 liters of vodka (assume 100 proof potato ethanol) = $11.00

A big chunk of that price is excise taxes, which are stiff. Excise taxes average ~40-50% of the cost of producing distilled spirits in the US.

However, dehydrating ethanol so that it can be used as fuel is energy intensive, so that number is probably pretty close to the mark after you add in the additional refining that would have to be done.