Because of the dry sump system they take a lot of oil.  Check your manual,
but I believe it's around 8 to 10 quarts, and don't forget to check the oil
when the car is idling and warmed up (and don't trust the oil gauge on the
dash).  I do know that Porsche now recommends Mobil 1 for all of it's cars.
Maybe not a great idea if your car has any oil leaks now, as synthetic oils
work their way into every nook and cranny, including existing leaks.
Because my car is older and has some leaks I use Valvoline Racing Oil, but
if I get those leaks fixed I may switch over to Mobil 1.

If you're changing your own oil please double check the amount and the
procedure.  You have to drain the tank and the engine, and then add a
specific amount before you fire it up.  Once warmed up you can top it off.

10 quarts of Mobil 1 0W-40.