Q400
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; Flight Crew Inflight Shutdown; General Declared Emergency
Aircraft
During climb checklist at 1;100 FT MSL; all engine parameters were green (within limits).  Later during climbout and after a few heading changes and a couple of frequency changes; we got a climb to either 16;000 FT or 20;000 FT.  Then we noticed the oil temperature on the number one engine in the red (122 degrees C).  After Maintenance checked the plane we were told that the oil was over serviced.  This causes the oil to cavitate (not cool properly).  We immediately ran QRH [which] directed us to reduce power 20 percent.  We also stopped our climb at 12;000 FT.  QRH said to give ten minutes for temperature to cool below 107 degrees C.  We contacted ATC that we had an issue we were working on and that we needed to stop climb; slow; run some checklists; and possibly turn back to [departure airport].  We sent ACARS to Dispatch. We also communicated with flight attendant's the issue; [and] to check #1 engine for oil; smoke; etc; as well as for them and passengers to stay seated.  We were back and forth on ACARS and attempts to OPS.  At ten minutes the temperature actually rose to 124 degrees C (oil pressure held steady at 66 psi).  QRH then directed us to 'engine fail/fire/shutdown' checklist.  We then shut down the engine and declared an emergency and made a turn for [departure airport].  We sent ACARS to Dispatch that we secured #1 engine; declared an emergency and were returning to [departure airport].  We communicated to flight attendants's the plan (everyone seated and fastened but no brace or evacuation).  I made PA to passengers that we had to shut down #1 engine as a precaution and that the plane flies very well on one engine.  I was initially PNF but then took control of the aircraft.  We communicated through ops once we were just a little closer other details (no fire; no evacuation; tug needed; etc.).  We were directed to QRC for other checklists to accomplish.  We had a very nice approach and landing; were met by fire and rescue (which did not use); tug; and Maintenance.
Q400 Captain reported shutting down #1 engine due to high oil temperature.  An emergency was declared and flight returned to departure airport.