[aerohead]

If I remember correctly,Class-6,7 and 8 trucks are tested up to 12-degrees of yaw as per some SAE Standard Practices.
Ford Motor Company reports wind averaged Cds for their cars,which represent yaw angles up to 8-degrees.
Baine Dayman Jr. of Cal Tech's Jet Propulsion Laboratory published an SAE Paper a few decades back which addressed crosswind effects to Cds.
Hucho dedicates a section in his books to annual statistical wind speed vs wind direction as pertaining to drag.
DOE/EPA has also published mpg effects of wind.
Each vehicle would have to be taken on a case-specific basis.There wouldn't be any patent expectation for yaw effects.