Here is SAE study:
http://www.nord-com.net/stoni/docs/SuTCAF.pdf
One of challenges would be EGR sizing.
Scania's E95 bus diesel cycle motors use apparently 26:1 compression ratio, fuel is bit special and as one can't use normal diesel pump, injectors etc. it is not so interesting as coverting diesel to spark plugs and having E85 as fuel.
Consumption will be more than with diesel fuel, because E85 will have less energy, but with turbo diesel difference would be only by amount of energy difference in fuel, but less consumption than converted gasoline motor.
Here it is illegal to make one's own E85 of course, like everything else is illegal, you always need to buy everything, very strong no to anything you do yourself, so that reduces a lot of savings compared to guys in US and other countries with legislation tuned for more individual rights than gov control. So better check the law before hoping to get relatively low cost transportation.