Engine oil serves two primary functions: 

• Lubrication of moving parts
• Heat removal from bearings, cylinders, and other components

Oil temperature reflects the thermal balance between heat absorbed from the engine and heat rejected by the oil cooler. When oil quantity becomes low, the volume of oil available for circulation is reduced. The pump draws from a diminishing supply, which reduces oil pressure. Simultaneously, the reduced oil volume means the system has less thermal mass to absorb engine heat, and the oil that is present circulates more frequently through the hot sections of the engine and oil cooler, resulting in elevated oil temperature. 

The combination of high oil temperature and low oil pressure is therefore a classic indicator of insufficient oil quantity. This is a potentially serious condition requiring prompt action, as continued operation with inadequate oil will lead to bearing starvation, overheating, and rapid engine damage.

Are normal indications during a long flight → INCORRECT. High oil temperature and low oil pressure simultaneously are never normal indications at any phase of flight including long flights. During normal steady-state cruise, oil temperature and pressure should remain stable within their respective normal operating ranges. 

Are indications that the engine sump has been over-filled → INCORRECT. An over-filled sump creates a different set of problems. Excess oil in the crankcase causes the crankshaft and connecting rods to whip through a pool of oil, generating excessive foaming, heat, and windage losses, which can actually raise oil temperature. However, over-filling would not produce LOW oil pressure because there is an excess of oil available to the pump. 

Are indications of low oil supply → CORRECT. The combination of high oil temperature and low oil pressure is the classic symptom pairing for insufficient oil quantity. Low oil volume reduces the pump output pressure and reduces the system’s heat capacity, causing the remaining oil to overheat. This paired indication should be treated as an emergency or serious abnormal condition and the pilot should follow the applicable emergency checklist, which typically calls for reducing power and planning for an immediate landing.

Are normal indications during circuit training → INCORRECT. While oil temperature may be slightly elevated during sustained low-level operations compared to cruise, high oil temperature combined with low oil pressure is never a normal indication during circuit training or any other phase of flight.