Honda RDX Owner's Manual page 427

Ambient Temperature
The oil viscosity or weight is
provided on the container's label.
5W-30 oil is formulated for year-
round protection of your vehicle to
improve cold weather starting and
fuel economy.
Engine Oil Additives
Your vehicle does not require any oil
additives. Additives may adversely
affect the engine or transmission
performance and durability.
Adding Engine Oil
421