that it works better other than their marketing material, but they say:
"Mobil 1 15W-50 is recommended for high performance vehicles including turbocharged and supercharged engines where a thicker oil film is desired.
Mobil 1 15W-50 is also recommended for older valve train designs that may benefit from a higher level of anti-wear normally not required for newer generation vehicles. Mobil 1 15W-50 will also provide better anti-wear protection for higher valve spring tensions in certain racing engines."