Service question

Hi

alrite guys/girls

I didnt get my car serviced from the main AUDI DEALER and the service light has obv been up for a while, but when do i no to service again?
how many miles on average do i have to service it?

Also by puttin on the aftermarket alloys (A8 Alloys) which im preety sure are not genuine, should this make a big difference in the MPG i am getting, i can already tell the difference in the weight of the wheels?


Many thanks


Javed

im defo using long life oil so i shud be okay for a while yet.
and thanks for the info on the wheels and regarding MPG.