The higher the compression an engine is the more thermodynamically efficient it will be.
There’s no way of getting away from it that’s a law of thermodynamics.
Ethanol is so high octane if you use it in an engine of high enough compression you’ll make up for it’s lower energy density, and so over all you get more power and better mileage.
That of course doesn't mean that an ethanol engine will be cheaper to run than a Gasoline engine it all will depend on the cost of ethanol, but the Federal Government subsidizes it’s sale in the U.S. and H.M. Government refunds the duty of 100% blends if it’s bought in the U.K. And then it’s really cheap to make so which is why the oil companies put it in their bulk products like 97 octane standard and 98 Premium, if you’ve noticed a drop in mileage it’s because you’ve got a car with an older larger displacement engine that was designed for torque on 100% Gasoline, and that meant low compression. 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 or even E98 and that’ll future proof your car as well. The most efficient way of all would be if you grew the corn for the ethanol on your own farm then moved that corn to you own distillery on the same farm 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.