I always use Shell V Power 99 in my 335i, it's now covered 114,000 miles 64k of them using shell V Power & it's still on original injectors with mot emissions now lower than when I bought the car six & a half years ago.
V Power costs around £1.40 a litre in my area, around 26 pence a litre more than cheapest supermarket fuel.
There was a fuel comparison on a tv programme called 5th Gear a few years back where they rolling road tested a golf GTI running different fuels. the old Shell V Power 98 ron showed a 6bhp gain over the the worst of the rest.
Link attached.
https://www.google.com/url?sa=t&sour...YHPuCfxaCPq8BT