How does the servicing work on the S4? Is it all variable based on the computer? As I'm planning on keeping this for a while, I thought I'd get my local Audi indie to do oil changes every 12 months which is about 4.5k miles for me, regardless of what the computer says. Also if anyone has servicing costs they don't mind sharing I'd love to see them so I can prepare. You know sell body parts, children, etc, that kind of thing!