I have an S3 and had to put 95 ron petrol in rather than the 97 Ron i usually use. Since then the car feels like its mis firing betwwen 4000 rpm and 5000 rpm, once i'm past 5k it just accellerates away as normal. does anyone have any ideaa why this has happened?

 

its called knocking or pinging. i would not recommend going under the recommended fuel octane, because of damage and performance lose that is assosiated with it. you bought an S, don't go cheap and with gas. if you want cheap get a toyota echo, you got a sporty car now pay the sporty price.

solution, just drive thorough this gas tank until its getting lower, when it does, just fill with the premium. and all will be well.