Follow the recommended tire rotation frequency for your
type of driving found in the “Maintenance Schedules”
Section of this manual. More frequent rotation is permis-
sible if desired. The reasons for any rapid or unusual
wear should be corrected prior to rotation being per-
formed.
FUEL REQUIREMENTS
The 3.7L/4.7L engines are designed to
meet all emissions regulations and provide
excellent fuel economy and performance
when using high quality unleaded “regu-
lar” gasoline having an octane rating of 87.
The routine use of premium gasoline is not
recommended. Under normal conditions the use of pre-
mium fuel will not provide a benefit over high quality
regular gasoline and in some circumstances may result in
poorer performance.
The 4.7 HO engine is designed to meet all
emissions regulations and provide satisfac-
tory fuel economy and performance when
using high quality unleaded gasoline hav-
ing an octane range of 87 to 91. The manu-
facturer recommends the use of 91 octane
for optimum performance.
238 STARTING AND OPERATING
•Do not change the thermostat for summer or winter
operation. If replacement is ever necessary, install
ONLY the correct type thermostat. Other designs may
result in unsatisfactory coolant performance, poor gas
mileage, and increased emissions.
Emission Related Components
Fuel System Hoses And Vapor/Vacuum Harnesses
When the vehicle is serviced for scheduled maintenance,
inspect surface of hoses and nylon tubing for evidence of
heat and mechanical damage. Hard and brittle rubber,
cracking, checking, tears, cuts, abrasions, and excessive
swelling suggest deterioration of the rubber. Particular
attention should be given to examining hose surfaces
nearest to high heat sources, such as the exhaust mani-
fold.
Insure nylon tubing in these areas has not melted or
collapsed.Inspect all hose clamps and couplings to make sure they
are secure and no leaks are present.
You are urged to use only the manufacturer’s specified
hoses and clamps, or their equivalent in material and
specification, in any fuel system servicing. It is manda-
tory to replace all clamps that have been loosened or
removed during service. Care should be taken in install-
ing new clamps to insure they are properly torqued.
Positive Crankcase Ventilation (PCV) Valve
Proper operation of the crankcase ventilation system
requires that the PCV valve be free of sticking or plug-
ging because of deposits. Deposits can accumulate in the
PCV valve and passage with increasing mileage. Have
the PCV valve, hoses, and passages checked for proper
operation at the intervals specified. If the valve is
plugged or sticking, replace with a new valve –Do not
MAINTAINING YOUR VEHICLE 315
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