1991 318i... oil leak, and what weight oil should I use?

[codyb]

I have a 1991 318i I just purchased with 178k on it.

It has a decent sized oil leak coming from the passenger side of the engine, seems like it's coming from the top part of it somewhere.

What should I be on the lookout for?

Also what weight oil should I run in this engine??? Would Rotella 15w40 (diesel oil) be a good choice?

[Geoff]

leaks from the front in that area are sometimes what is known as the profile gasket.  its part of the general timing case,  which gets leaky after high miles.  unfortunately, this is not the easiest thing in the world to address, and if you do address it,  you pretty much have to address the timing gear if there are any problems with that.  you dont want to do this twice if you can avoid it.  I refer to all timing componants,  chain, gears, tensioner,  guide rails etc.
                 Rotella 15/40 is a good choice, imho.  I like the Rotella synthetic too.
                                                                Geoff
                       ps-dont use synthetic in a leaker tho it leaks even more...

[DesktopDave]

TheM42 is a leaker, no doubt about it.  Hopefully it's not the timing gasket...might just be the chain tensioner crush ring, easy to swap that out.  Could also be the large paper gasket behind the chain case (it's not quite so easy to swap that one out).

Rotella is good stuff, can't go wrong with that.  Use the weights BMW specifies in your owner's manual.