There's nothing magic about any oil, Mobil 1 included. Synthetic olis
may be less prone to polymers being sheared, but metal particles &
other contaminants affect the oil no less than "ordinary" oils.

Synthetics are NOT made for economy; they are more expensive to use.
The POTENTIAL saving lies in decreased engine wear, NOT extended
change-intervals.

  Changes should still be made at engine manufacturer's recommended
intervals. ESPECIALLY DIESELS, which blow gritty (abrasive) carbon
particles past the rings into the oil.