What viscosity grade should I use for my engine? For my gearbox?
The use of the correct viscosity grade guarantees optimum engine or gearbox protection. The choice of oil should generally be based on the recommendations of the manufacturer, who designed its parts according to a given oil viscosity. If in doubt, choosing a viscous lubricant limits the risk of wear, though at the expense of performance.
An oil grade is defined by two elements:
→ A winter grade (0W, 5W, 10W, etc.) representing ignition problems at very low temperatures. A 0W grade will be more fluid when cold than a 5W grade.
→ A hot grade (20, 30, 40, etc.), corresponding to the oil's viscosity in a hot engine. A grade 40 oil, more viscous than a grade 30, provides a greater degree of engine protection, but also lower performance due to viscous loss.