Chevron Delo 400. FWIW, I used to run Delo 400 in the SDL. Changed to Mobil 1 and the noisy lifters are much quieter now. Go figure.

This in an interesting thread because the S420 is due for it's first oil change under my care and I was thinking of going with Mobil 1.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD