Date: 201809
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Aircraft component: Oil Distribution
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; Flight Crew Inflight Shutdown; Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft; Procedure; Human Factors
Primary problem: Aircraft

Narrative: Flight was delayed due to completion of service check; about 1 1/2 hours late. Upon nearing the end of the runway and ready for takeoff a low oil level status message came up. Having seen these messages for years and always having enough oil/flight time I believed we had enough. However; I still pulled out the QRH and read through the appropriate message in the status message section having only glanced at the oil level on the display. I don't recall the number that I read on the screen at the time but I had the impression from what I read that we had enough and told the First Officer that we were good and we'll just keep an eye on it and if we needed oil we could get some at our destination. I put the QRH away and shortly after was cleared for takeoff; without looking at the oil level again I changed the screen back to the status message page. At the start of the takeoff roll I glanced at the engine instruments as usual to ensure everything was in the green; and all numbers were approximately the same for both engines.Climbing through 10;000 feet we noticed the oil pressure was decreasing and going yellow. I then rechecked the oil quantity and noted it was at 15%. I pulled out the QRH and checked for possible caution messages. Shortly after; I instructed the flying pilot to increase speed and reduce power to see if that would have an effect on the oil pressure. It increased slightly but overall kept decreasing. At 20 PSI we received a L ENG Oil Pressure warning message. I turned to the appropriate page and followed the procedure which led to a precautionary engine shutdown; [advising ATC]; and return to field.After the flight mechanics inspecting the aircraft told me that there appeared to be an oil leak within the engine; later after they had taken it to the hangar I was told over the phone that there was definitely a leak somewhere in the engine. Then; while waiting around the flying pilot and I discussed the events and at that time they made the remark that they saw 15% oil quantity once we got onto the runway but because I said we were good said nothing.An oil leak in the engine; running late and trying to rush knowing we had a longer route then usual due to ATC reroute for weather along our normal route. Poor communication between me and the First Officer prior to takeoff; specifically using ambiguous terms; i.e. saying we were good with the oil quantity versus saying what I saw on the gauge when I looked at it and what I read in the QRH.Slow down; especially when I feel pushed to get going. Say what I'm seeing and reading to ensure both of us see the same thing or catch a discrepancy; and also to arm the First Officer with knowledge so that if I make a mistake; misinterpret; or simply miss something; they are in a better position knowledge-wise to speak up.


Second narrative: First flight of the day. We got to the airport being notified that the airplane was still in the maintenance shop and would be an hour and a half delayed. Once the airplane was towed to the gate; I did my walk around and didn't notice anything unusual. Captain was trying to catch up on some of the delay we already had; so we set up the aircraft rather quickly; without putting safety in jeopardy. MCD [main cabin door] closed; started taxiing to Runway XX. I was Pilot Flying and we were holding short of the runway waiting for our release at this point. Right before we started rolling to line ourselves up; I noticed a status message pointing out a low oil level in the left engine. I saw the Captain was already looking in the manual at this point; and told me we were good to go for 1 leg; and decided we'd ask for an oil fill up once [at destination].We departed on a right downwind and climbing. Going through 8;000 feet he notices our oil pressure starts dropping at a rather fast rate. He pulls up the manual while I'm still flying and says that as long as our oil temperature remains in the green; we are good to continue. A few minutes later; climbing through 14;000 feet; the 'L ENG OIL PRES' warning message came up along with the aural warning. I kept flying the airplane; leveled off at 14;500 feet as he was slightly reducing the power on the defective engine. He then ran the QRH and advised me we needed to shut down the left engine. We followed the procedure; stabilized the airplane; and advised ATC of our intention to return to field. We turned around direct ZZZ and descended to 10;000 feet. With an excess of fuel; we decided to hold for about 45 minutes in order to get below MTOW in order to land. Right before our final descent; Captain became Pilot Flying and we proceeded to a safe landing on Runway XX. We were able to taxi to the gate on our own; and then deplaned everybody.I believe with the rush caused by the initial delay; the Low Oil Level status message before takeoff should have been looked at closer. I did not second guess his answer; and after talking about it past the incident; I believe I remember seeing a 15% level on the L ENG; where he can't seem to remember what number he definitely looked at. On initial climb; he looked at the level again; and we definitely both remember seeing 15% at that point as well. I believe once in flight we did everything in compliance with the procedure and the purpose of bringing the airplane back on the ground safely. After the fact; Maintenance told us that there was indeed an oil leak in the left engine.Once again; I should've second guessed what he looked at; being that 15% is definitely on the lower side of it. The rush to catch up time is something I encounter quite often; and don't necessarily understand. Operations and Dispatch are always working on taking care of this side of the airline. So in this case; I definitely believe asking for a couple more minutes to look into the issue would have helped. After fact; Captain talked to Maintenance and [we] were told that indeed an oil leak was found in the engine. So even though it was an unfortunate event; it luckily happened soon after departing and we were then able to return to field with plenty of fuel and beautiful weather.


Synopsis: CRJ-700 flight crew reported the engine oil quantity was decreasing after takeoff the engine and oil pressure started dropping.