See also:

Front/Rear Axle Fluid
For normal service, periodic fluid level checks are not required. When the vehicle is serviced for other reasons the exterior surfaces of the axle assembly should be inspected. If gear oil leaka ...

Tire Terminology And Definitions
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American Petroleum Institute (API) Engine Oil Identification Symbol
This symbol means that the oil has been certified by the American Petroleum Institute (API). The manufacturer only recommends API Certified engine oils. CAUTION! Do not use chemical flushes in y ...