Jeep 2005 Liberty - Manual (Page 277)

Light spark knock at low engine speeds is not harmful to
your engine. However, continued heavy spark knock at
high speeds can cause damage and immediate service is
required.
Poor quality gasoline can cause problems such as hard
starting, stalling and hesitations. If you experience these
symptoms, try another brand of gasoline before consid-
ering service for the vehicle.
Over 40 auto manufacturer’s world wide have issued and
endorsed consistent gasoline specifications (the World-
wide Fuel Charter, WWFC) to define fuel properties
necessary to deliver enhanced emissions, performance,
and durability for your vehicle. The manufacturer recom-
mends the use of gasoline that meets the WWFC speci-
fications if they are available.
Reformulated Gasoline
Many areas of the country require the use of cleaner
burning gasoline referred to as Reformulated Gasoline.
Reformulated gasoline contains oxygenates, and is spe-
cifically blended to reduce vehicle emissions and im-
prove air quality.
The manufacturer strongly supports the use of reformu-
lated gasoline. Properly blended reformulated gasoline
will provide excellent performance and durability for the
engine and fuel system components.
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