How often should I change the oil in a 2005 Porsche Boxster S?

I just purchased it used with 28k miles on it I figured I would use Mobile 1

THEY SAY 10,000 MILES W/MOBIL1 I REC. EVERY 7500. NOTHING BETTER FOR A CAR THAN FRESH OIL EVEN BETTER IF ITS EARLY.

Thanks for your help!