Silver cap Mobil 1 15W50 is supposed to have the highest ZDDP level of all the Mobil 1 oils. The 10W30 and 10W40 Mobil 1 High Mileage are also supposed to also have a very robust add pack.
I use the 15W50 year round and never have any issues with it. I`m actually considering going with Valvoline conventional 20W50. I guess I`m wondering just how important PAO synths really are. I keep seeing cars running in the 200k-400k mile marks with no lubrication issues whatsoever that have been using dino oils all their lives.