12. Shall I use higher viscosity grade for high mileage engines?
Viscosity of the engine oil must be selected according to instruction manual provided by vehicle manufacturer. All permissible viscosity grades for specific ambient temperatures are listed in the corresponding lubrication chapter. If vehicle manufacturer allows use of higher viscosity grade, then you can do so. However, unwarranted choice of higher viscosity grade without OEM permission may lead to abnormal engine operation or even to the failure of
Vehicle manufacturer recommends properties of the applicable lubricant according to characteristics of the engine. Recommended viscosity is determined primarily by diameter of the lubrication channels, clearances and design specifics of the engine.