Date: 201409
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: Regional Jet 900 (CRJ900)
Operator: Air Carrier
Operating under: Part 121
Flight phase: Climb
ATC / advisory: TRACON ZZZ
Aircraft component: Powerplant Lubrication System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Flight Attendant (On Duty)
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft; Procedure
Primary problem: Aircraft

Narrative: We had an aircraft with MEL's 79-XX-XX (Eng. oil lvl Indic) and MEL 79-YY-Y (oil replenishment system.) We kept the same plane for our next Flt. We had a MX man come and request the logbook but never mentioned why he needed it as I was getting out of the aircraft for a post flight walk around. When I got back; he was gone and they were boarding the aircraft. After all the passengers were on board; I mentioned to the FO that MX still had not returned the logbook. MX arrived shortly to say we need to deplane because they over serviced the oil and were cleaning it up and they had to run the engines without passengers on board. He also did not understand why they boarded the aircraft after their Manager called Ops to hold off boarding. I called our Dispatcher and they knew nothing about this. I explained to the passengers the issue before we deplaned them and said it should not take too long and we will be on our way again. MX ran the aircraft and we boarded the people and MX came out with the logbook and said it was good to go. I then got out of the aircraft and did another walk around to verify all service doors were closed etc. We taxied out to the runway and I briefly checked all our engine indications were in the green and equal before taking the runway. While on climb out about 30 miles east I noticed the left oil temp in the red. We caught it before the master warning. I called for the abnormal checklist and immediately reduced the left engine to idle and turned the aircraft back and declared an emergency. As per the checklist we monitored the oil pressure and it continued trending down and we agreed as long as it continues cooling; we would not shut it down. We were able to ACARS 'emergency and returning' to our Dispatcher. During our descent it ended up back in the green on about a 10-15 mile final. We landed overweight and met all of the requirements for not being considered a hard landing or a hard de-rotation. We briefed the passengers about the situation and let them know we have another aircraft. Once boarded the other aircraft I let them know we appreciated their patience and we were going to give them free refreshments enroute.


Second narrative: The event occurred after the aircraft reached 10;000 feet. The pilots called the flight attendants and explained that there was going to be a precautionary landing due to high engine oil temperature; and told us to prep the cabin for landing. We landed safely and taxied to the gate. Everyone was safe and deplaned via the air bridge.


Synopsis: CRJ-900 Captain and Flight Attendant describe a precautionary return to the departure airport for high engine oil temperature. The engine oil had been replenished prior to departure and some spilled due to MEL's for Engine Oil Level Indicator and for Oil Replenishment System.