Originally Posted by Immo
I think I read somewhere with the 5.7 Hemi 89 is recommended.
Probably the Owners Manual [free from www.jeep.com]
or Owners Guide
Guide: "We recommend you use of
89 octane or higher for
optimum performance but
87 octane is acceptable"
Manual: "This 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."
Believe there's a TSB for Hemi driveability if using 87 rather than 89.
It should note midgrade, as at higher altitude you don't need as high a number as at sea level.
Typically a dime a gallon more expensive, and your Hemi will thank you will a bit more deposited rubber on the roadways.