158k high mileage oil recommendations ?

[piper6909]

Forgive me for reviving an old thread, but I didn't want to start 'another oil thread.'

So it's time for an oil change and I'm having a hard time finding the recommended (According to the manual for my climate, both above and below 50 degrees F.) 10w-40 grade in Mobil-1.

I know that now Porsche recommends 5w-50, but I didn't see any charts based on climate, and I find it hard to believe it's good for all climates, especially not for below 50 degrees F.

From my research on here I've seen people using 0-40, 10-30, 5-50, and other grades, some of which aren't even listed in the manual. Why such a variety of preferences when the manual seems quite specific?

Nonetheless, since 10w-40 is harder to find, am I safe using 5w-40, which is more readily available?

Thanks in advance!