Re: 156 jtd and mobil1 turbo diesel oil?
As far as oils at dealers/good indies go, they usually only have 2 (perhaps 3 at really big places) huge drums (1000ltr? or so) of oil, which do nearly all veghicles, turbo and N/A.
I could name a very well respected indie for porche, mercedes and BMW which has ouil supplied by 1 major company and 2 types does all. (same for VW, skoda and Audi)
Its the viscosity and synthetic properties which determine engine type or iul life - 10or20k intervals.
You just need to be sure its not too thin for the motor/turbo.