Roland,
The Mobil1 15W-50 is THE Mobil 1 oil to use if you are choosing Mobil 1. There's as many opinions on this as anything else. However this blend has the highest levels of Zinc and Phosphorus of all their offerings. The challenge is, it's not always easy to find. I've found mine in the past on sale at WalMart (I still have 2 or 3 5 quart jugs on the shelf) at about $22 each. I'm sure it's much more now.
Attached was downloaded moments ago from the Mobil 1 website. Go to page 3.
I've used Mobil 1 exclusively in my car since the engine was rebuilt 20 years ago during the restoration. However, it's only been the past 10 years that the Z & P levels were much of an issue and then I started paying attention to these. Only that 15W-50 has them at a high level, but there are other oils that have an equal or higher level. There are also Z & P additives you can get, and in reality, what's wrong with that? If you add it, or they add it at the factory, what's the difference?