Thread: Predator ?
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Old 12-18-2009, 10:05 PM
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Vehicle: 2009 Dodge Ram 1500
Trim Level: Laramie
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Engine: 2009-2010 345ci (5.7L) Hemi V8 390hp 407lb/ft
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here's the quote from page 386 of the 2009 Ram 1500 Owner's Manual

Quote:
The 5.7L engine is designed to meet all
emissions regulations and provide satisfactory
fuel economy and performance when
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, as it will not provide any benefit
over regular gasoline in these engines.

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 considering service for the vehicle.
so the only reason that higher octane gas is not recommended is because there aren't any benefits from it (and of course, this is just for the stock tune)
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