Mobil 1 15W-50 Synth.
Better in every way than obsolete conventional oil.
If your 911 was built today, Porsche would only suggest Synth.
Forum wanna-be oil experts obsess about a single component for motor oil: ZDDP. The logical fallacy that the forum wanna-bes keep committing is this: they assume that in order to meet the new SM/SN requirements, the ONLY thing the oil companies did was reduce the amount of ZDDP in their oils, leaving everything else unchanged. That's ridiculous. Oil companies have been working on additive packages for decades and testing how well they work in preventing wear. The reduced levels of ZDDP in these oil have been replaced by other, sometimes proprietary, additives that work as well or better. Moot point since Mobil 1 15w-50 has a 1300 ZDDP rating anyway!
And before anyone says it,
No leaks.
Synth leaks are another internet myth.
Debunked.
It's amazing how long misinformation lives on.
People still think carrots are good for the eyes.
It is a wives tale. When synthetics first came out, like 30 years ago, they could affect seals and cause leaks. Oil manufacturers quickly figured that out (they work closely with car manufacturers) and put additives in to stop that.
https://www.walmart.com/ip/Mobil-1-15W-50-Advanced-Full-Synthetic-Motor-Oil-5-qts/20713647
http://forums.pelicanparts.com/porsche-911-technical-forum/971645-who-runs-non-zddp-fortified-synthetic-oil-not-20w-50-a.html