I read some studies in 2001 about different companies fuels, octane, cleaners, additives etc.
Off the back of that i have always filled my cars with shell unleaded or diesel.
I would then fill with vpower about every 5-10 fills or if it was my second 'fun' / performance car, always with vpower.
I always get better mpg with vpower, but not enough to offset the cost as such, but for it's cleaning properties.
Needless to say I've never had any issues of bad dpf's, deposits, gunk build up or premature wear in any of my cars, so continue that way for the next 20 years too.
Incidentally shell has never been more expensive than any other competitor, not including supermarket stuff, which isn't im the same ball park