Car Questions

Clear all

Engine Oil


Topic starter
Which engine oil should I buy.
Topic Tags
5 Answers
Topic starter

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.
Topic starter

Oil Testing

Testing "High Mileage" oil claims.

This is not "real world" testing and so should be taken with a grain of salt. Nevertheless, the tests are very rigorous, and various interesting results came out of them.

Topic starter

Oil Specifications

The American Petroleum Institute (API) is the North American lubricant testing standards body.
The latest oil specifications can always be found on the American Petroleum Institute's website:
These are current classifications (as of May 2023)
International Lubricant Specification Advisory Committee (ILSAC) is an international lubricant testing standards body.
The GF-6A starburst:
The GF-6B shield:
Europe has its own system, called ACEA categories.
Topic starter