Foam weatherstripping would be way cheaper and easier to test the ideas with. It worked on my helmet when I was riding my bike a lot so there might be a very tiny gain if you get it placed just right on a car.
Somehow I think it would be hard to measure a change even with a coastdown test but I could be wrong ....
i've come across something similar on the web. turbulator tape seems to be comonly used on gliders and is somewhat similar to vortex generators, although not entirely.
the way i understand these things work is that they're placed just ahead of a sepparation bubble wich is a point where laminar flow seppatates from the wing. the additional drag they cause is smaller than the drag the bubble would cause.
for the turbulator to function this point has to be exactly determined.
there might be potential for this on cars, but the very exact placement and potential to small to measure gains might might make this difficult for most people to implement.
on the other hand this turbulator tape seems to be nothing else than a thick sawtooth patterend tape, so people willing to try might be able to make it themselves. or use the stuff used on gliders if you have access to it.... afterall if you compare the width of your car's rooftop to the span of a glider youd only need a small leftover.
Here is the organization that is was presented at (maybe) :
14th Asia Pacific Automotive Engineering Conference (APAC-14)
August 5-8, 2007 / Renaissance Hollywood Hotel / Hollywood, California, USA http://www.sae.org/events/apac/
While the name has changed to reflect a broader audience, the 14th Asia Pacific Automotive Engineering Conference still embodies what the original International Pacific Conference on Automotive Engineering (IPC) stood for. A successful, historic event since 1981, APAC serves as a way to promote automotive engineering development worldwide, choosing this year's theme, "Impacts & Opportunities for the Global Automotive Industry," to focus on five major technology subjects:
* Powertrain Technology
* Driver/Vehicle Interface, Information and Assistance Systems
* Vehicle Design and Manufacturing
* Transportation Challenges in Emerging Markets
* Vehicle Dynamics and Intelligent Control Systems
SAE is pleased to host this premier automotive engineering event with patronage by FISITA.