I find this a really interesting subject, moving to E10 has been in the offing for a long time, all cars built since 2011/2012 have to be able to run on it. The numbers that can’t use it have now reached a point where it can be introduced without causing upset. Ethanol does not like aluminium and can cause some plastics and rubbers to dry out and become brittle, it can remove debris in fuel lines that will cause blockages, anything that uses a carburettor will not be fond of E10.
There is a cost to mpg of up to 3% it is estimated, felt mostly in small capacity engines, the ones we have been encouraged to buy over the last few years. In fact WLTP testing note a 3.8% difference in economy from E0.
Ethanol is a similar price to petrol so there will be no cost saving/increase in the price per litre of E10 at the pumps, we will just be filling up a few more times a year.
I could go and on and on….