re. Question for QLCC users

[TM]

True about the oil-
My car ticks incessantly on even 10W30 Mobil 1, but is
quiet w/ 15W50.

What do you all think- are the older cars designed for a
higher viscosity oil? I know that both 10W30 and 15W50 are
not out of spec for my car according to the manual and the
Bentley, but I hesitate to use something like the new formulation
Mobil 1 0W40, which is the recommended oil for the 1.8T and 2.7T
engines.

Taka