"For the higher grade fuel doubters".....but the video shows that 99% of road cars don't benefit one jot? Of course there are engines that do benefit, like big power turbos, but I don't think anyone said otherwise?
As for the "cleaning benefits", I would take all that with a pinch of salt. The uncombusted fuel touches hardly any of the engine. If you want a cleaner engine, service it properly and use decent oil. Oil is what removes contaminants from the engine.
I used to use Sainsbury's 97 octane, as it's supplied by BP and is often the same price, or cheaper, than "regular" from the likes of Shell etc. MPG was no different from V-Power after careful testing.