The cylinder head is no doubt "dried out" which means a valve job may be in your future. At the very least, you'll need new valve stem seals. These can be done with the cyl. head attached to the rest of the motor. The valve guides may or may not need replacing. Only a talented MB tech could determine that.

As time goes on, you'll likely find yourself using oil. Consider the above.

The biggest problem of all with any car idle this long(not just 91 300SE) is all of the "electrical gremlins" that may start to haunt you.

I've gotten good service out of mine. Good luck to you.

PS - this site has been around since 1999. There have been tons of posts on the M103 motor your MB has. Search the archives.

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