Not necessarily the case. My '97 Mark VIII ran well ONLY on 92 octane or higher which was [u:af821e28d0]recommended[/u:af821e28d0] in the owner's manual. It wouldn't run right if I used 87 or 89 octane. And a '95 Continental I owned was premium fuel ONLY (not just recommended, but [u:af821e28d0]required[/u:af821e28d0]!).
I've been thinking about running 89 octane in my '98 5.4L Expedition. Haven't decided yet.
Saturday, February 11th, 2006 AT 9:42 PM