The car came with 0w 40. You need an oil that has a summer weight of 40. So if you can't find 10w 40 and that's what you wish to use then go on amazon and buy it. 0w40, 5w40 are what's usually recommended. If you stray from the weights porsche suggests don't be surprised when you have an expensive problem on your hands. Don't use "the store next to my house was out of x brand" as an excuse to throw whatever in your motor.
Oh, and read this :
Frequently Asked Questions about Motor Oils / LN Engineering - Knowledge Base LN Engineering
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