I have a 270,000 km SUV with the OM651 diesel, on cols start it rattles like a bucket of bolts and then shuts up as the oil pressure builds up. after that is fine. car drives perfect, no lights.
now it is due for an oil change. as this is a high mileage engine, what viscosity do you recommend ? for Australia, not extreme cold here.
I am considering doing the tensioner. anything to look out for ?
i am also considering doing the chain as well, i don't want to pull the motor and do the guides as thats a monster job.
in the past on other cars, i have done chain replacements by attaching the new chain to the old one and slowly cranking it through, obviously with everything still linking meshing on the top cams and so on.
anyone done this before ? any pointers ?

Thanks in advance.

Havnt done it but dont forget the chain tensioner plug (forgot the name for it), theoretically those can go out as well and are heck of alot easier to replace. EDIT maybe thats what ya meant by the tensioner, been long week already.

As for oil stick with the specs or join the chaos that is oil recommendation threads.

Thanks, yeah I have made the mistake of not putting MB229.5 oil before in my other AMGs and it never ended well
The chain tensioner plug is the tensioner thing I was talking about.
Are they as easy to pull and swap as people make it out to be ?

Go with what the owner's manual tells you for oil. Otherwise you are opening up a can of worms by asking in a forum. One guy here will even tell you to put in the oil that is made for big rig trucks LOL

I think the guy you are referring to is talking about vehicles with Diesel engines. That's not as dumb an idea as you make it out to be. The oil recommended by Mercedes (MB229.51) is at best a compromise between what is best for the engine and what is good for the emissions equipment and mileage bragging rights.

My (Diesel) GLK can use oil meeting MB228.51, and there are oils that meet that spec as well as the CK-4 spec, the best of both worlds, IMHO.

If your 300SE has flat tappets, one of the best oils you can get for it (IMHO) these days is Shell Rotella T-6, a Diesel oil with higher levels of zinc than gas engine oils have these days. (Why? because zinc poisons the latest catalytic converters.) T-6 used to carry a spark ignition rating, (SM), but they removed it when the newest converters became incompatible.

YMMV...