Back in the 1970s when cats first appeared, MB published that every engine they'd ever built would be fine with unleaded fuel.

Some interesting (if shrill) info on this subject:
http://www.thenation.com/doc.mhtml?i=20000320&s=kitman&c=1

__________________
Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles