Which guideline should be followed to determine the grade of oil to be used in a vehicle?

Choosing the grade of oil for a vehicle is critical for ensuring optimal engine performance and longevity. The engine manufacturer's recommendations are the most reliable source to determine the appropriate oil grade. These recommendations are based on extensive testing and engineering design specific to the engine's components and operational conditions.

Each engine is designed with particular tolerances, clearances, and performance characteristics in mind. The correct oil grade helps in maintaining adequate lubrication under various operating conditions and ensures that the oil can withstand the heat and pressure generated by the engine. Using an oil grade that aligns with the engine manufacturer's specifications contributes to achieving maximum efficiency and effectiveness, reducing wear and tear, and prolonging the engine's lifespan.

While national oil standards and oil manufacturer recommendations provide useful information, they are often broader and may not be tailored to the specific engine model. Additionally, while a mechanic's advice can be valuable, it should ideally align with the engine manufacturer's guide to ensure it meets all necessary performance requirements. Thus, following the engine manufacturer's recommendations is paramount for optimal vehicle upkeep.