Found this on
Toyota's website: "Turbulent air increases drag, which adds wind noise and reduces efficiency. Camry features small, specially placed design features called vortex generators to help smooth things out. Not only do these help Camry maximize its efficiency, they help keep things quiet inside the cabin too."
I think this refers to the small VGs manufacturers today use on exterior mirrors and taillight and headlight lenses (my Prius has a single VG on each headlight, molded into the clear plastic), but they are VGs nonetheless, and if they didn't do
something the manufacturers wouldn't go to the trouble of using them. That said, they are very small in size and number. Slapping VGs on the back of a car willy-nilly is an exercise in futility.
I'm remembering just now, too, the wing on the back of the SRT-10. It had a trough on the underside, about an inch long, that ran the width of the wing.
Hard to see in this picture (not my truck), but it's there. I seem to remember Dodge claimed the trough gave a slight improvement in aerodynamic efficiency versus a spoiler with no trough. With the standard tonneau cover in 2006, however, the wing was redesigned and the trough was gone.