For me, the whole fuel discussion/debate really depends what you want to get from it.
Personally, a performance fuel isn't going to make your car suddenly more powerful/quicker. It may run a bit better but I think that a lot of the benefits are more subtle.
My old
Mk1 Leon TDi had done 220,000 miles when I finally got a new one. It had the rock solid PD engine and probably did the last 100,000 miles on BP Ultimate. It just seemed to like it. Ran well and never had any issues. Just before I sold it I checked the EGR valve and it was pretty clean. Can't say it was specifically the fuel but I've seen some really clagged up ones and do think that fuel choice kept the car healthy.
I think that a lot of the benefits are longer term and less obvious. As
@SuperV8 says - it's more to do with lubrication and protection of the inner workings of the fuel system and engine.
If you have a company/fleet/PCP type car that goes back after 2 or 3 years with 50,000 miles on the clock, I don't think you'll be affected (or bothered) so much.
It's the people with higher mileage cars who pick up the bill for new parts and extra work. My
Mk3 Leon had 60,000 miles on it and now it's on 103,000. I like to put Shell V-Power through it because it seems to like it. I intend to keep the car and would like that extra `protection`. This car also has a DPF and I hope that a decent fuel helps keep that healthy as well.
Due to lockdown and a lack a Shell garage locally, I've been using Tesco diesel. I have a fuel additive that is meant to be the same as the major fuel folk and I'm currently using that. Rather than an extra £10 per tank of V-Power, the additive costs about £1. My car has been chipped but is still giving me 55mpg on local runs and 68mpg on motorway runs. I'm not saying that's just the fuel or additive but I'd like to think that it helps.
Of course, the fuel companies are very secretive about what they add and how it all works. Some say it is snake oil and just a placebo product. I do believe they add value but it's very hard to measure.
For me - I think performance fuels
help, but I think we're all different in how we measure that or view the perceived benefits.