Here's the invoice from the dealer.
From what I can tell the tech. is telling me he reprogrammed the computer and to run premium fuel only in the Mustang GT.
Anyone care to explain?
Sounds to me like Ford may have come out with some new software that may of included a fix for spark knock when cold, which may be less evident when higher octane fuel is used. Where I work, they do various software upgrades throughout the year and the only people that know about these updates are us and the dealers we are working with (once they are made aware). Then all of the new machines that are being built get the new software and the older machines out in the customers hands would only get the newest software if they replaced a controller and then downloaded the software available from our Performance Website. Anyway, long story, but I thought I should explain my reasoning. Anyone else care to add anything?
It sounds to me like they updated your PC with the latest software, and they're supposed to be telling you to try a different fuel brand (ie, if you're using Shell, try BP), and maybe try the next level up in octane if that doesn't solve it.
Use only Chevron or Sunoco 93 octane... Shell and others (and some Chevron ) have too much alcohol... yes, cheaper, cleaner, bla-bla.. BUT need much more VOLUME; thus, if car not tuned for specific fuel, knock.