NO supermarket fuel. Stick with Shell VPower and ok to use normal Shell every now and again. Get it cleared out of rubbish fuel and let the good stuff work, probably get better and better as the VPower cleans it up.

Doesn't the ST run rich on V-Power? I didn't think the ECU was mapped to run anything over regular BP or Shell 95? I have used V-Power a couple of times but it doesn't seem to make a difference to performance or fuel economy?

I suspect it does run a little rich, yes it was mapped for 95 but VPower has better cleaning agents and the ecu tables can populate to adjust a little, I have used both and not found any noticeable performance difference, I might run on 95 for a while and see if I get less soot in my exhaust, it is always a little dirty after a week, but also I am on MT so that may affect too, my journeys are local so not ideal, I do a weekend blast but thats only a few miles to clear it. My RS1800 was super clean that was the Zetec Engine which was Lean Burn by nature, never anything in that exhaust.

i use tesco super 99 now my car runs so much better!

Thats interesting to hear that bout the fuel, will bear it in mind. Thanks