Engine oil viscosity

Lubricants behave differently at high and low temperatures.

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.

To ensure that your vehicle performs optimally, your oil should retain a certain level of viscosity in all weather conditions:

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.