Oil Quantity/Oil Temperature/Oil pressure
I think a few of the statements made have been a bit ambiguous.
Normally, if fitted, three oil system instruments can tell you lots about the situation. Low Oil Pressure accompanied by rising Oil Temperature will almost certainly be accompanied by falling Oil Quantity. Reduced oil quantity means the available oil gets circulated more often which will cause the higher temperature (less oil to carry away the heat and less time to cool) High oil pressure accompanied by low temperature means, usually, oil cooler flap is too far open. It always wise to look at all info available to trouble shoot. Checkerboard's comment about low oil temp means you are about to run out of oil may not necessarily be true, it will all depend on where the temperature sensor is in the system. Some people run their cars out of water and see no rise in water temp. that is because the sensor relies on the temperature of the water in which it is immersed to transfer the heat to the sensor probe. Oil system temp probes work the same in some installations.