The Slipperiest Car on the Road | Blog | Tesla Motors I'm reminded of the scandal with the manufacturers providing fuel economy numbers to the EPA. They all make their own numbers up (or, use some sort of testing that is peculiar to each manufacturer and are not equally-weighted, like an independent measurement would be). Only when they are truly ridiculous do they get called out for making up fictitious numbers. It's good to see coefficients of drag getting independently measured on the same equipment. Kudos to Car And Driver. Now we can really compare them. The Mercedes CLA250 measured number of 0.30 seriously calls into question Mercedes' own claim of 0.23, which is a significant difference. By comparison, right in line with our understanding of Elon Musk - who gives it to us straight, warts and all - the Tesla claim is 0.24, and Car And Driver measured 0.24.