I hate these oil posts, but will respond anyway.

You have a '91 model W126 car. Same as me, just a bigger engine.

I've used conventional oil for many years and have taken more than one car past 300K with it. I used synthetic oil once(don't ask me why) and all it did was create leaks. It's known for doing this; however, in it's defense, it may be less likely to do so in the cars it was intended for - newer models.

Use a Mann, Mahle-Knecht; Hengst oil filter and the prescribed amt. of oil(conventional in my opinion). Do as Larry Bible suggests, changing it hot and often. The oil in my MB gets drained every 1500-2000 miles.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"