89 Octane Minimum

5.7L HEMI engines recommend 89 octane for optimal performance.

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Nearly every entry level car in the 1960s.

They had modern OHV designs and decent compression. Regular (leaded) gas was 89 octane. When it was banned in the 80s gas stations offered unleaded 89 and people bought it for their 87-spec cars as a "treat."

Also what Grasscutter wrote-- there were other some semi-modern Dodges that took 89, even an Intrepid IIRC.
 
All 5.7 HEMI’s with automatic transmissions recommend 89, but can operate on 87.

When equipped with a manual, they lose MDS and REQUIRE 91 octane.
 
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