Here are some symptoms in my '84 380 SE:

1) High fuel consumption

2) Starts at the flick of a switch in the morning. But when warm, it takes a couple of turns of the engine - not terribly bad though.

3) Once in a while, when warm, if I let go of the ignition immediately when starting, it seems that the car wont start but then it kind of "catches up" and starts

4) If I am trying to warm up the engine at 1000 rpm or so, it seems I loose control over the revs and it varies / hunts from 2000 rpm to around 700 rpm. This does not happen always. Normal idling is at 500 rpm.

I really want to ensure that the car does not use any extra fuel. I am willing to sacrifice performance if I can somehow throttle down the fuel consumption.

Any advise on what I should do is greately appreciated.

The first things I would think of would be the idle control valve and/or the oxygen sensor.

Your idling problems sound like a faulty idle control valve, but I don't think that would hurt the fuel economy. A malfunctioning idle control valve is giving our 380SE some cold start issues at this time; we just need to get a new one.

-Sam