Ethanol always burns cleaner than Petrol/Gasoline, that’s why Governments make everyone buy a blend. It's also is better for the country’s trade balance as ethanol can be made locally. If pure ethanol is used in an engine of compression as high as 15, 16 or 17 to 1 it can be more powerful than Petrol/Gasoline. The carbon in it was fixed by photosynthesis from atmospheric CO2, so it can slow, stop and perhaps reverse the effects of climate change. An engine of 10.5 to 1 should return similar mileages as petrol/gasoline in an engine of 10.5 to1, Older cars designed for straight gasoline rarely had compression this high so they’ll do poor mileages.
If you get a dedicated ethanol engined car with a compression of 15, 16 or 17 to 1 it will do much better mileage and have better power. But you have to use pure ethanol. An ethanol engine is more thermodynamically efficient. But that isn’t what’s going to make a dedicated ethanol engine cheaper to run than a Petrol/Gasoline engine it all will depend on the cost of the fuel, but ethanol is cheap to make. Ethanol engines of high compression will cost little if anything more to build from new, but converting from a finished car will be expensive. But anyone who can work on a Petrol/Gasoline car will be able to work on an ethanol car as they are identical except for the compression and new cars shouldn't be any more expensive.
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 engines) 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.