Everyone loves the sleek, sexy lines of a sports car, but there is so much more to it than just looks. Those smooth lines were designed to maximize the car's aerodynamics, or the ability of the vehicle to move smoothly though the air as it cruises down the road. But what are the most aerodynamic cars on the market today? As we go through these cars, we'll be talking a lot about drag coefficient. If you're unfamiliar with the term, it refers to a car's aerodynamic efficiency.

While there's a lot of math that goes into determining a car's drag coefficient, the most important thing to remember is the lower the drag coefficient, the more aerodynamic the car. Volkswagen XL1 This entire car was designed for fuel economy, and while it's not available in the United States, the mind-bogglingly low 0.186 drag coefficient might make it worth the import costs, if you're looking for a car that will get you more than 300 miles per gallon but has no front grill or side-view mirrors. Those features were traded to make room for that insanely low drag coefficient, making this the smoothest car on the road today.

Toyota Prius While it doesn't generally top anyone's list for sleek or sporty cars, the Toyota Prius actually has one of the lowest drag coefficients in on the market. Paired with its hybrid engine, it allows this little car to get an average of 50 miles to the gallon.

Tesla Model 3 Elon Musk's electric cars are already breaking the mold, but they're also some of the most aerodynamic cars on the road. The Model 3, when tested, clocked a 0.21 drag coefficient. While you're not worrying about gas mileage when driving a Tesla, that low drag definitely contributes to a smoother ride.

Audi A6 Audi is one of those brands that is normally associated with luxury, but it's still managed to create a decently aerodynamic luxury car. The A6 tests out at a 0.26 drag coefficient, which is surprising for its normally boxy body style.

Jaguar XE Everyone loves the sleek lines of a good Jaguar, but the XE provides an amazingly smooth ride due to its 0.26 drag coefficient. This particular model has been described as the most advanced, refined and efficient car that Jaguar has ever created.

Mazda 3 Mazda has always had a great track record for creating sleek and sporty cars, but the Mazda 3 takes the metaphorical cake. It's won the title of most aerodynamic car in its class, most commonly determined by testing in a wind tunnel, and boasts a drag coefficient of 0.26.

Tesla Model S OK, we may have a bit of a crush on Tesla's unique design and sexy lines, but they are still among some of the most aerodynamic cars on the road. The Model 3 we mentioned earlier is a bit smoother, but the Model S isn't too far behind, coming in with a 0.24 drag coefficient. That's not too shabby for an electric car.

BMW i8 We can't write a list of sleek cars without mentioning BMW at least once. The i8 model may not be the smoothest car on the road, but it's definitely in the upper echelons, with a 0.26 drag coefficient.

Nissan GT-R Everyone loves a good sporty Nissan, so it's no surprise at least one has made it onto our list of aerodynamic masterpieces. The GT-R is one of the fastest-accelerating cars on the market today, pulling a 0-60 in less than 3 seconds. This is possible, in part, thanks to the 0.26 drag coefficient. With a top speed of 196 mph, this sleek beauty will blow past you if you blink.

Mercedes-Benz C-Class You can't talk luxury without Mercedes-Benz. With a super-low drag coefficient and top-of-the-line aerodynamics testing, the C-Class series is one of Mercedes' smoothest and best-performing cars on the road today. Aerodynamics is one of the biggest things engineers consider when designing a new car. The sleeker the car, the lower the drag and the higher the fuel efficiency. Now that you know which cars are the most aerodynamic, will that influence your next car purchasing decision? Let us know in the comments.