I have run 3 Audi's on 87 Octane - no issues. the crossfire - I'll keep putting the good stuff in - I fill the tank once every 2 to 3 weeks - so what am I going to save - isn't going to get me a vacation in Hawaii or even the Jersey shore. Good read - and I believe it wouldn't hurt the car.
Never killed the Audi's and we are on our 4th.