My local merc dealer puts fully synthetic in my c222 cdi engine.

I think the use of fully synthetic or semi synthetic is more to do with the
age of your engine.as the older engines were not designed for these oils
which can be much thinner at start-up.

alec

Chris <chris@thingysrealm.myftp.org> wrote in news:20060414152129.634cf931
@isis:

My mate used it all the time is his brand new 205 DT. He used to drain it
out and put the Dino oil back in before a service, then reuse the synthetic
stuff because it was still clear. The Dino stuff went black after a few
humdred miles and the synthetic lasted thousands of miles before it
coloured. He swore by synthetic, I think it was Millers. This stuff
http://www.fasteronline.co.uk/oil-xfd-synth-5-l-p-745.html
The Peugeot dealership he used was in Dunfermline and the one time I went
up with him to pick up his car, I heard the comment that his car was
cleaner in all ways when it came in than it was when it went back out.
If you popped the lid and looked at the engine, it was shiny as per
Military shiny. He is in the Navy after all.  

Any pug from 2003 onward can use fully synthetic oil. Before that best
to use semi. That's what we do at our dealership.