That is a question, it really depends on many factors and if it’s a newer car it would or should do better on e10 than an older car but you will get less mpg from it over e5 but the e5 is more expensive. either way it’s another scam to make us pay more for less.
Where it will make a difference and did on my last car (20 plate) was with the power when you put e5 in, it was super quick and seeemed a lot smoother at higher revs. Not surprising though as it had 182 bhp and a vtec engine, so the high content fuel burnt better. It didn’t give a better mpg or it wasn’t that noticable.
So I’d put the occasional tank of e5 in if i was going to be doing a long journey or driving country roads. Omg that was so fun, kind miss it. Now i got a different car, Since june I’ve only put e10 in it. Maybe when price of fuel comes back down i will try some e5 in it and see.