Jeep 2008 Commander - Manual (Page 334)

using high quality unleaded gasoline having an octane
range of 87 to 89. The manufacturer recommends the use
of 89 octane for optimum performance. The use of
premium gasoline is not recommended. Under normal
conditions, the use of premium gasoline will not provide
a benefit over high quality regular and mid-grade gaso-
lines, and in some circumstances may result in poorer
performance.
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 are spe-
cifically blended to reduce vehicle emissions and im-
prove air quality.
The manufacturer supports the use of reformulated gaso-
line. Properly blended reformulated gasoline will pro-
vide excellent performance and durability of engine and
fuel system components.
334 STARTING AND OPERATING