These are the slipperiest cars on the mass market.
When it comes to modern car design, with both performance in mind and as emissions rules tighten, aerodynamics are incredibly important. Aerodynamic drag uses more fuel to push the car through the air so the car needs to be as slippery as possible while still being practical to use. For race cars where the only aim is to not be slowed down by air resistance, it's a slightly different ballgame and it gets really difficult when the vehicle needs to carry passengers and be practical day to day. For body designers working with both form and function, aerodynamics becomes an art.
The effect of the car moving through the air is measured by its drag coefficient and that value is denoted as Cd. The lower the Cd, the better, and in an ideal world right now a modern car needs a coefficient drag number measuring under 0.30 Cd. These are some of the cars that currently better that number with a Cd of 0.26 or lower.
What's particularly interesting about the Q50 is that once you start getting high up the trim and options list, wider tires and different ride heights start to change the Cd rating. Even then, the Q50 still does very well and Infiniti is keen to impress how much it's worked on reducing drag using its partnership with the Red Bull Racing team.
The Mazda3 is proof that looks and character don't have to be sacrificed for good aerodynamics. The most attention to detail has gone into underneath where not only is there an effective underbody at work, but the suspension components are also protected by well-placed aerodynamic aids.
Hybrids tend to have an advantage as they tend to not need as much air flowing under the hood for their smaller engines to keep cool. Like many of the cars on the list, Kia uses active grill shutters to minimize that even more. Kia has also put a rear diffuser and wheels designed to be more aerodynamic to good use and, on top of all that, we love that the Optima Hybrid doesn't scream at you that it's a green car.
The original Honda Insight actually preceded the Toyota Prius and the first Insights had better gas mileage than several generations of Prius after it was discontinued. Now, the insight is back and doesn't look like someone took some acid and imagined what cars of the future would look like. In fact, it doesn't look like a car being marketed for being economical despite its hybrid drivetrain and very competitive Cd rating.
It's no surprise the Prius comes in strong when it comes to cutting through the air as the Prius is all about fuel economy. The latest generation actually beats the previous model by 0.02 Cd with improvements to the roofline and using extra panels underneath the car to stop air swirling into places that don't help the cause.
Mercedes has been keen on aerodynamics for decades, and some of its larger cars can compete in their slipperiness through the air with cars featuring much less surface area. The S-Class has a lot going on, but we particularly appreciate the big trick grill. Air flowing into the radiator is an important function to keep an engine cool, but Mercedes uses the shutters on the grill to only direct air into the engine compartment when needed.
Hyundai is one of the surprise entries on this list, but the Hyundai has been making huge strides in how it guides air around its cars. Like Mercedes, Hyundai has figured out the air being pushed into the radiator isn't always needed and has developed an active front grill that works in three stages.
Surprisingly, Tesla is not running a class-leading Cd number although the Model S is still remarkably efficient and it's worth bearing in mind the Model S is a lot bigger than the Model 3 that it shares its looks with. Tesla has worked hard to aerodynamically optimize the car, especially around the front wheels - an area that can generate a lot of extra drag.
In 1984, Mercedes put a lot of effort into making the E-Class more aerodynamically efficient and achieved a Cd of 0.27. Now, over 30 years later, the E-Class has gotten bigger while that number has dropped. In terms of coefficient drag, just a couple of extra points makes a big difference so it's hard to not be impressed by what Mercedes has achieved here.
The Model 3 is smaller than the Model S so there's less bodywork for the air to rub up against, but we're still surprised it's not actually better considering companies like BMW, Mercedes, and Hyundai have figured out that air pushing against the flat radiator and around the engine bay is a big drag, and an electric car doesn't have that issue to deal with at all.
Special editions built specifically to help companies meet range-wide emissions standards are a fact of life now. Like Mercedes and Hyundai, BMW has embraced the active grill shutters as well as developing their wheel design to not be as much as an effect on the overall drag of the car. 0.22 Cd is very impressive, even before you consider that the 5 Series is a big lump of a car.
Mercedes-Benz claims the new A-Class Sedan has the lowest drag of any production vehicle worldwide. Details include the front area of the new A-Class being reduced to just 2.19 meters squared, the underbody being fully enclosed, and Mercedes has made sure the headlights seal flush and tight to the body panels.
With the amount of work, effort, and pride Mercedes takes in its approach to aerodynamics, we hope to see a 0.20 Cd non-special edition production car at the beginning of the next decade.