Being more thermodynamically efficient isn’t what going to make an ethanol engine cheaper to run than a Gasoline engine it all will depend on the cost per mile but ethanol is cheap to make. The Federal Government subsidizes ethanol’s sale in the U.S. and H.M. Government refunds the duty of 100% blends if it’s bought in the U.K. You can of course modify the engine fitted to your car, if it’s an older engine it’ll need it by now anyway. If you need a total engine rebuild you might as well do it for E30, E85 and that’ll future proof your car as well. The most efficient way of all would be if you grew the feedstock on your own farm, straw, cardboard pulp or elephant grass. Then moved it to your own distillery within yards and then sold it from your own fuel stop.
Most Governments who listen to their scientific advisers realize we’re in the throws of climate change, there’s no doubt about that. Whether it’s our fault people argue, but doesn’t matter, we’ll be the ones experiencing the effects. Responsible Government's will need to show they have been doing something not just pandering to the needs of big business. Internal combustion engines are more thermodynamically efficient the higher the compression that engine is. Not only is ethanol carbon negative it is much higher octane than pump Petrol/Gasoline and will if used in a high compression engine be more powerful, more economical and more thermodynamically efficient. So it can be a better motor fuel. If you’re green you can feel good about saving the world, if you’re not you can have the personal satisfaction of buying a better cheaper motor fuel.
All modern S.I. engines start with settings remembered in the ECU, settings to start the engine using it’s fuel easily. Immediately it fires it continues running with feedback from the sensors. ECU's do accommodate for wear in the moving parts, but they're actually programmed to keep the engine in the most economical and powerful state of tune within the mandated exhaust perimeters.
The U.K. Government knows that burning fossil fuel is a major cause of climate change and they've all got a duty of care, that's why all the petrol for sale in the U.K has some ethanol in it, that's also why Briton has finally put some bio-fuel duty rebates in place. Essentially anyone in the UK can get a duty rebate it just has to be a 100% bio-fuel it CAN BE ETHANOL (used in spark ignition engines) or BIO-DIESEL (used in pressure ignition engine) and you must have been charged some road duty for it. The problem is buying 100% bio-fuel is difficult, the oil companies have no reason them sell them, none of the price would actually be for them. The government isn't advertising it (why would they, it would cost them revenue). The 25,000L/year allowance is designed to be just what a private individual would use for personal use.