You know it's hard economic times when a manufacturer sells you a hocus-pocus-sounding stick-on skin for your car and suggests it increases your miles-per-gallon efficiency: and that's exactly what SkinzWraps is. It also potentially increases your car's speed too, but that's not such a selling point when everyone's worried about the value of the dollar in their pocket.
Apparently the product is inspired by shark skin—for sharks, the complex interlocking scale-like denticles on their outer skin layer create a very smooth hydrodynamic surface, making shark swimming much more efficient. It's an idea used for a long time now on golf balls... which the Skinz product more closely resembles, if you ask me. Maybe "inspired by shark skin" sounds sexier.
Golf balls achieve their amazingly long flights in part due to the hundreds of dimples on their surface. Many a scientist will tell you that the dimples reduce aerodynamic drag experienced by a golf ball in flight by stalling the air that's passing near a dimple, and creating improved boundary-layer separation and reduced drag vortices—or something like that. That approximate answer's because the absolute physics are really hard to compute: In an effort to redesign the simple golf ball, for example, Arizona State University researchers are throwing serious supercomputer power at the problem. It's all a question of positioning and sizing the dimples to get an optimal aerodynamic beahviour.
SkinzWraps just encloses your vehicle in a regular-array of small dimples—computing how that affects each car's aerodynamics would be a mega-computing task indeed (note that simulating just a tiny portion of a golf ball's aerodynamic behaviour for a fraction of a second takes hundreds of hours of computer time.) But the company claims that by improving the aerodynamic slipperiness of your vehicle through reducing drag, and thus lowering the load on your engine, SkinzWraps actually adds 18 to 20% to the miles-per-gallon rate of the car.
And that's a very bold claim indeed, since it effectively cuts the fuel cost of driving by a big margin. Despite the scientific claims of the company (they even quote modified Reynolds numbers, a measure of boundary-layer air flow behaviour,) this 18-20% figure hasn't been independently verified. It'll depend on the particular shape of each car and the wind speed and driving speed of each journey. During one test, the skinned-up car's MPG efficiency apparently decreased when it got dirty—Suggesting that the dimples were working, but when they filled up with normal road-dirt they stopped improving the aerodynamics and the MPG dropped.
But if it actually works, which in principle it actually could—albeit with unpredicatble results—then it'll open up lots of research for improved car aerodynamics. And that'd be great for your wallet, and the environment too.