I have had my 1981 300SD for 2 weeks now and absolutely loke it. 98K miles and so far I have changed the following small things:
1. Primer pump.
2. Fuel hoses under tank.
3. Steering pump fluid.
4. Power windows white thingy to move it up and down.

Going home today, noticed oil pressure was not going above 2 bar. Idled there and flinched just a little when I stepped on it a little. Temp OK. stopped car looked under hood and under car, OK. Saw oil sprayed on cam then decided to take back roads and keep RPM close to idle. Got home, disconnected battery came to this forum, read for about 1 hour. Went back out, conneted battery, started car and now idled below 1 bar. Turned it off, looked under the hood, cleaned and replaced contacts on everything in the fusebox while I was trying to figure out where to start. Saw a loose vacuum to that black thingy on top of the valve cover (connected to throttle linkage - what is that thing - vacuum connection looked loose) and fixed it. Started the car and everything was OK. I have driven it around town for 10 miles since then and it still OK.

What was that all about? Is it a fuel pump failure warning, (100K miles now) or just an electric glitch. Previous owner changed oil at dealer the day I bought the car and I have the paperwork - I am changing oil again tomorrow and sticking with RotellaT like PO.