Originally Posted by Wildsailor
I am not entirely sure but what made me think of it was the idea that the SFE package, which comes with wheel covers that block off the air passage through the wheels, is worth 2 MPG highway. The 18" package is wider and may add to the frontal area. If the Focus is that sensitive that a wheel cover can make 2 MPG difference then wider tires and wheels may have an impact.
Two cars side by side, one with 16" and one with 18", doing a coastdown would verify.
In the meantime if those that are struggling to get to the numbers being posted for FE are all 18" Sport Package Titanium then that would start to fill in a pattern.
I'm not sure that it is the wheel covers where they gained 2 mpg on the EPA cycle but rather the grille shutters and a few other tweaks which were more beneficial but were later applied across the line, so I'm not sure why the SFE still has a 2 mpg higher rating.
I've gotten 42.1 mpg approximately at 65 mph over 470.1 mi and 11.176 gallons of gas this past weekend in my SEL hatch with three people plus over night bags, water/ other luggage, etc.
So would the SFE sedan really have gotten 44.1 mpg at the same time/ conditions? I doubt it.