Then swap the sensor, that's an easy job.
I don't know of an easy way to measure oil viscosity, but I found that Blue was using more once the oil went a brown colour.
Near or inside the pump is a pressure release vaove that limits the max pressure the oil pump delivers, too high and the oil can damage bearings as it flows though too fast. This valve has a seat, dsometimes it's rubber, and can lead to probelms with oil pressure untill the pump is flowing fast enough to overcome what is effectively a leak.
You could put a pressur egauge on, even as a temp thing, to check what's going on.
Alternatively use an oil with a cold-start additive for peace of mind.