Originally Posted by Power Surge
The way I read that verbage in the manual, is that it means in areas where regular is considered lower than 87 octane, to use fuels labeled premium for better performance (especially in high altitude areas).
That's what I understood from it. Unless your racing your Focus in the Daytona 500 I think I'll stick with 87. I average 34 mpg between city and highway using 87. These engines werent designed for high octane fuel like a higher performance engine would be, hence the manual stating to use 87. My fathers Acura states to use 93... He's not out there looking for racing fuel