It is not always a good solution, you might need the help of a professional as it depends according to the situation. If the vehicle is brand new, it might not be that advisable as the moving parts have accommodated a certain amount of pressure. If the vehicle is old and the vehicle starts producing more noise than ordinary or more vibration then it is advisable to take it slightly to a higher viscosity as the gap between the moving parts and their parameters might have increased slightly during that period.