Ford 1998 Ranger Owner's Manual page 160

Filling station information
Ensure correct automatic transmission fluid is used for a specific
application. Check the container to verify the fluid is MERCON and/or
MERCON V approved. Some fluids have been approved as meeting both
MERCON and MERCON V requirements and will be labeled as such.
Fluids labeled as meeting only MERCON or only MERCON V
requirements must not be used interchangeably. DO NOT mix MERCON
and MERCON V. Transmission fluid requirements are indicated on the
dipstick or on the dipstick handle. Refer to your "Service Guide" to
determine the correct service interval.
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