Want to know which cars have the slipperiest shapes? Look no further than luxury sedans. Like the forthcoming new BMW 3 Series, which – as the automaker has now revealed – boasts a drag coefficient of just 0.23.

That may not make it the most streamlined vehicle hitting the market, but it's pretty darn close, with just a tenth more drag than the new Mercedes A-Class sedan. BMW's figure ties the slipperiness of the Tesla Model 3's shape, and bests the Model S' 0.24. The only BMW more streamlined is the 520d EfficientDynamics, which comes in at a Baby Benz-tying 0.22.

That's pretty impressive, and it didn't come by accident. Among the tests through which the automaker has been putting its new compact sedan includes extensive development at the BMW Group's Aerodynamic Test Centre in Munich, where full-size vehicles had their shapes honed for minimal drag. Under the new Worldwide Harmonized Light Vehicle Test Procedure, it even had to wind-tunnel-test each of the wheel options it will offer on the new sedan.

Along with aerodynamic testing, the Bavarian carmaker has been running prototypes for the next 3 at the Nurburgring and its Miramas test track in southern France.

It's run prototypes through the electromagnetic field at the Hoover Dam, the punishing heat of Death Valley on the California / Nevada border, and the freezing cold in Arjeplog, Sweden. And it's simulated over 12,000 driving maneuvers on computerized test beds, too.

All the while it's labored to keep the prototypes from our prying eyes by disguising them with camouflage wraps and body cladding, painstakingly applied in the basement of its R&D center in Munich. Wrapping each car takes a full day, with engineers required to refit window decals to hide the interior at the end of each test day. Here's hoping it all proves worthwhile. The all-new BMW 3 Series will make its global debut next month at the 2018 Paris Motor Show.