Date: 201306
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Aircraft component: Powerplant Lubrication System
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Human factors: Training / Qualification
Second reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Rejected Takeoff; Flight Crew Returned To Gate
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: The Captain and I performed a RTO procedure. I was the Flying Pilot and the Captain was the Non-Flying Pilot. We were instructed to depart Runway XX. We crossed the runway hold short line and the Captain transferred control of the aircraft to me. I advanced the thrust levers; stabilized the engines at 40% and then further advanced the engines to takeoff power. I made the 'Check Thrust' callout and then the Captain placed his hand on the thrust levers. As we accelerated down the runway the Captain noticed that the oil quantity of the number one engine was decreasing at a rapid rate and he called 'REJECT.' I immediately transferred control of the aircraft back to the Captain and then informed Tower that we were rejecting on Runway XX and to please 'Standby' as we decelerated to a stop on the runway. When the aircraft came to a complete stop I then made a PA to all the passengers to 'PLEASE REMAIN SEATED; PLEASE REMAIN SEATED.' After I made the announcement to the passengers to remain seated I asked the Captain; 'What happened; why did we reject?' He stated that he saw the left engine oil quantity falling quickly. Tower then asked us if we needed any assistance. The Captain and I felt that we didn't so I informed them that we did not. We then proceeded to exit the runway. As were exiting the runway the Captain spoke with the flight attendants and ensured that both they and the passengers were OK. Everyone was fine. After we exited the runway we stopped again on the taxiway to further assess the situation and to then perform the RTO checklist on the back of the QRH. We determined that the aircraft was in fair working order and that the situation was stable enough to return to the gate normally without any assistance. We taxied the aircraft back to the ramp and parked at the gate without any further incident. We shut the aircraft down and then performed the Parking Checklist. We then coordinated with the Gate Agent and flight attendants to further stabilize the situation.


Second narrative: On takeoff roll; noticed oil quantity steadily decreasing through 40; rapidly down to 23 percent; without slowing down. As the quantity went down through 35-30 percent (at maybe 40-60 knots; not sure) oil pressure and temperature were normal - but then they would be until the oil quantity reach zero or very near it. I began considering the options and balancing the threats: clearly it's safer to go flying rather than perform a high-speed reject in almost all cases - but the trend looked like oil was leaving the engine at a rapid rate and we were going to hit zero oil quantity right at or shortly after rotation; which is also a pitch change and could potentially move oil around - which could be either good or bad. My consideration now involved taking an airplane flying with zero oil in the left engine at a high pitch angle; low airspeed; and high power setting. And a First Officer flying who isn't off high minimums yet - he's great but this is still a factor. And; of course; I've got a plane that has a boatload of stuff wrong with it and quite frankly I'm not trusting Maintenance at the moment. NOT a good situation. Made decision to reject takeoff at 23 percent with the quantity still decreasing; prior to making the 100 knot call. Looked up; saw 110 knots while stating 'reject' and taking the controls. A very 'normal' rejected takeoff was performed; I must say that while I failed to raise the speedbrakes (auto speedbrakes MEL'ed; new RTO procedure; and the heat of the moment) it was a remarkably calm; clear moment once the decision was made and the training really did help.


Synopsis: A B737 Captain rejected the takeoff near 100 KTS after seeing the oil quantity rapidly decreasing.