Engines - Oil System (RR) 
- Company Limitations - Engine Oil Quantity
- Boeing - Flight Crew Considerations for Engine In-Flight Shutdown
The oil system provides pressurised oil to lubricate and cool the engine main bearings, gears and accessory drives. The oil system also provides automatic fuel heating for fuel system icing protection.
The oil system is pressurised by a main (engine-driven) oil pump (driven by the N3 rotor). From the pump, the oil flows through the main oil filter where contaminants are removed. The main filter cannot be bypassed. The L/R OIL FILTER EICAS advisory message displays to indicate the main oil filter is clogged. The oil flows through the oil cooler (where fuel is used as the heat sink) and is then delivered to the engine main bearings, gears and accessory drives.
A scavenge pump (also driven by the N3 rotor) returns the oil to the reservoir. Prior to the reservoir, the oil flows through a scavenge oil filter. If the scavenge oil filter becomes clogged, the oil bypasses the filter.
When impending bypass of the scavenge filter occurs, the L/R OIL FILTER EICAS advisory message is displayed.
Oil pressure, temperature and quantity are displayed on the secondary engine display.
Oil Pressure is measured (downstream of the pump) prior to entering the engine. When the oil pressure is at or below the variable limits (normally 18 psi), the EICAS indication changes to amber.
The L/R ENG OIL PRESS light illuminates and the L/R ENG OIL PRESS EICAS caution message displays to indicate oil pressure is low.
Oil Temperature is measured after leaving the engine, prior to entering the reservoir.
There is no minimum oil quantity limit (no amber or red line limit). There are no operating limitations for the engine oil quantity and there are no flight crew procedures based solely on a response to low oil quantity.
