[Fusion]

Welcome to the club! In general, the first thing that you can do to get better mpg would be to replace the stock air filter with a performance air filter (k&n), or if you have the cash, go for a complete Cold Air Intake system.

 

[Fusion]

You'll have to look around to see what intakes you can find that will fit, and i'm sure you won't have any trouble finding stores online that sell them. I know that K&N sells one called the Typhoon (I think somebody on here bought one for about $300). It shouldn't be to difficult to install, it's mostly a swap of parts.