A CRJ200 Captain declared an emergency and returned to land after the aircraft's left engine oil became erratic and dropped to the 30-50 PSI range. Maintenance reported five quarts of oil in the engine.

Narrative

After a normal takeoff;with normal oil pressure; I noticed the left oil pressure reading erratically. It was between the 45-60 PSI range and very erratic. As we climbed to 10;000 FT. The oil pressure dropped to the 30-50 PSI range and more erratic. Eventually the pressure was low enough to give the triple chime and 'oil pressure' aural. At that time we ran the QRH procedure and conferred with Maintenance on communication 2 radio along with my Dispatcher. I made the decision to return to the departure airport with the Dispatcher concurring. Due to the fact that we decided that an overweight landing was in order due to the engine issue; as well as the fact that we would be landing flaps 20 (a precaution in case the engine required subsequent shutdown inside the marker) I declared an emergency. I then briefed the Flight Attendant in accordance with our FOM procedures; relaying all necessary information. We were vectored for a right base visual approach. An uneventful landing was made by me as I was the flying pilot; with a sink rate of approximately 100 FP per minute. The fire rescue personnel inspected our aircraft and then we taxied to the gate. We deplaned using normal procedures. There were only 5 quarts of oil in the engine according to Mechanic.