Thou shalt obey the manufacturer
The engineers that designed your engine know what it requires. They have a chosen an oil specification which will meet the demands of your engine. The specification consists of an oil viscosity, and a performance standard. This specification is provided to you in the owner's manual, in the maintenance and care section. Sometimes, it is printed on the oil filler cap. Check manufacturer website for the most current information.
- Always choose an oil that meets, or exceeds, the specification.
- Always use the viscosity recommended in the manual, regardless of distance on the odometer.
- Do not change oil viscosity based on temperature, unless stated in the owner's manual. (older or international cars)
- Forget anything the car dealer tells you.