DGraham

I have a 04 Lupo Sport, when i picked the car up i filled it with Shell Optimax as i have a Octavia before that and it run alot better with it. After about 4 days the engine checklight come on and would not go off i have a fault code reader and the code was 17598 (Linear 02 Sensor / Reference Voltage Incorrect Signal), i kept knocking the light off but it was about 10 to 30 mins and it was back on. I took the car back to VW as its still under warrenty they said they had knocked it off but it would come back on as whoever had changed the backbox had chopped the cat out. This was aload off rubbish only the back box had been changed, after putting up with the light for a few weeks i thought why wast money on expensive fuel when it wasnt right and filled it up with normal fuel. After a couple of days it went off on its own and has never been back on since i have used normal fuel, put optimax back in and on comes the light. Has anyone had the same problem?? I have heard ppl say on here the sport runs better on Optimax. Also i think i have a dodgey fuel gauge it sometimes doesnt go out when the gauge is over quater any1 with the same?? Thanks