To find an approximation, you'd need to consult:
* Independent automotive testing websites or magazines: These often test vehicles and publish aerodynamic data, though finding one specifically for the 2006 Fusion might require some searching.
* Automotive engineering databases: These are usually subscription-based and may contain the data you need.
Expect any value you find to be in the range typical for sedans of that era, likely between 0.28 and 0.32. Keep in mind that this is just an estimate.