An oil can, in effect, be characterised by its viscosity, its flow resistance or by the thickness of its oil film. Viscosity varies according to temperature in the following way: the higher the temperature, the more fluid and less viscous the oil will be.
It should remain fluid at low temperatures (to make cold starts easier) and viscous at high temperatures (in order to provide protection and sealing). The grades that have been optimised for each of your oils are detailed in your service manual.