When I first got my S3 I used Optimax, but then I had to fill up a few times at a non-shell non-SUL garage so just had to use normal unleaded.
To be honest, I couldn't even tell the difference!
Now I fill up with regular unleaded as the rule rather than the exception, although every now and then I do 'treat' the car to a full tank of Optimax /ubbthreads/images/graemlins/smile.gif
Alex.