FORD 1999 Explorer - Manual (Page 208)

Do not use supplemental engine oil additives, oil treatments or engine
treatments. They are unnecessary and could, under certain conditions,
lead to engine damage which is not covered by your warranty.
Change your engine oil and filter according to the appropriate schedule
listed in the Scheduled Maintenance Guide.
Ford production and aftermarket (Motorcraft) oil filters are designed for
added engine protection and long life. If a replacement oil filter is used
that does not meet Ford material and design specifications, startup
engine noises or knock may be experienced.
It is recommended you use the appropriate Motorcraft oil filter (or
another brand meeting Ford specifications) for your engine application.
BRAKE FLUID
Checking and adding brake fluid
Brake fluid should be checked and
refilled as needed. Refer to the
Scheduled Maintenance Guide for
the service interval schedules:
1. Clean the reservoir cap before
removal to prevent dirt or water
from entering the reservoir.
2. Visually inspect the fluid level.
3. If necessary, add brake fluid until
the level reaches MAX. Do not fill
above this line.
4. Use only a DOT 3 brake fluid
certified to meet Ford specifications.
Refer to Lubricant specifications in the Capacities and specifications
chapter.
MAX
Maintenance and care
208