Whoops! Well, anyway, I think my point still- energy content is not the only factor- as diesel can get much more than 12% improved fuel economy. Diesel runs at much higher compression ratios, which is a good part of the increased economy. There's other things too, like the lack of a throttle plate which reduces pumping losses.

Ethanol is being operated in the same engine as gasoline.

That's correct, hence my point. I'm not comparing to anything else, I'm thinking of the Flex Fuel engines that can use E85 and regular gasoline.