I agree with DemonSVT.
Same thing happened to my Tour, until I installed a DiabloSport chip.
The chip requires 91 octane or higher for the best performance.
With the chip installed, I am using 93 octane now, and getting the same MPG as 89 octane.
Even BETTER highway MPG.
Pete... 98.5 SE Sport Duratec ATX (P66L) Black Clearcoat on Greystone DOB 11/21/1997 DOP 12/25/1997 PIAA 510 Super White Driving Lights SVT CAT-BACK EXHAUST (No Resonator) DiabloSport Chip (LPQ4) - Engineered To Raise Hell Too many other mods to list... Sounds sweet, runs quick... Crazy Horse Dyno @ 121.4 WHP/129.6 TQ
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