Nay.
1st Issue- The air is already turbulent on the skin of a car, you're only making it more turbulent.
2nd Issue- The air in the first 2 inch layer of the car is only .05% of the air being moved about by your car. There is a lot of air moving 10 feet on top and to each side of your car, and for hundreds of feet behind it. A .05% change in the air movement can not create a noticeable change in the drag.
3rd Issue- There is a certain amount of drag created by the "Vortex Generation" itself. In order to make a positive difference, the newly invigorated air would somehow have to not only overcome the drag it just produced, but it would have to somehow create less drag down stream. On any modern automobile, this simply isn't going to happen. Maybe some crap box from the 70's or 80's, but other than that, you'll only be shooting a squirt gun at the Hoover Dam and expecting it to improve it's performance.
4th Issue- Cars are not airplanes, they follow vastly different aerodynamic rules. Just the same......Please explain how a reduced stall speed equates to a lower drag? It is flim flam pseudoscientific jibberish designed to baffle and confuse. In fact, to generate more lift you must by definition create more drag.....think about it.....if by making more lift and LESS drag, you'd reach a point where a 400 foot wing span on a piper cub would be the ultimate flying machine with almost zero drag and the ability to lift hundreds of tons with a 95hp motor going 450 MPH getting 50 MPGs doing it. Yeah, that makes sense.
With VG's in respect to fuel savings, you need to give it some serious skeptical analysis and then just......