GMC 1993 Safari Owner's Manual page 317

6. TRANSMISSION SERVICE
Change the transmission fluid and filter every 15,000 miles (25 000 km).
If the vehicle is mainly driven under one or more of these conditions:
In heavy city traffic.
Where the outside temperature regularly reaches 90°F (32°C) or
higher.
In hilly or mountainous terrain.
Frequent trailer pulling.
Uses such as taxi, police, delivery or other commercial service.
If the vehicle is not used mainly under any of these conditions, change
the fluid and filter every 30,000 miles (50 000 km). See "Automatic
Transmission Fluid" in the Index for more information.
7. FUEL FILTER REPLACEMENT* -Replace the fuel filter at the specified
interval or sooner if clogged.
8. SPARK PLUGS REPLACEMENT* -Replace spark plugs with the type
listed in Section 6. See "Specification Charts" in the Index.
9. SPARK PLUG WIRE INSPECTION* -Clean wires and inspect for burns,
cracks or other damage. Check the wire boot fit at the distributor and at
the spark plugs. Replace wires as needed.
10. ENGINE TIMING CHECK AND DISTRIBUTOR CHECK -Adjust timing to
underhood label specifications. Inspect the inside and outside of the
distributor cap and rotor for cracks, carbon tracking and corrosion. Clean
or replace as needed.
cap and lines for damage or leaks. Remove fuel cap, inspect gasket for
an even filler neck imprint, and any damage. Replace parts as needed.
11. FUEL TANK, CAP AND LINES INSPECTION* -Inspect the fuel tank,
12. ENGINE ACCESSORY DRIVE BELT INSPECTION* -Inspect belt. Look
for cracks, fraying, wear, and proper tension. Adjust or replace as
needed.
*
An Emission Control Service
7-9