We have all heard the idiom "This … has the aerodynamics of a brick" at one time or another and it is not by accident that the expression has become universally popular among automotive enthusiasts. It turns out, in fact, that when it comes to aerodynamics (which in a car determines a number of characteristics, including but not limited to top speed, fuel consumption, and noise inside) you pretty much cannot do any worse. How do we know? Well, some really smart people invented the ‘drag coefficient', which is a useful number to measure the frontal area resistance of a solid object in air or liquid. When this solid object is a brick, the number equals 2.

Back to cars, ever since people recognized that cars and carriages are not the same thing, car manufacturers started to pay more attention to aerodynamics as part of their efforts to make their cars go faster, be more stable, and look better (although the latter turned out to be way more than a function of wind resistance). All in all, in the last half a century aerodynamics has had a crucial role in shaping our concept about the attributes of a car's exterior.

So what are the 5 cars of today, which are most brick-un-like in terms of their Cd (the accepted designation of drag coefficient)?

5. Opel Insignia

So it is not only beautiful but also efficient in the way it slips through the air. The 2009 European ‘Car of the Year' award winner has been a total hit so far with its sales in Europe and is well-received on the US market, as well, where it appears with a Buick badge. Of course, the Insignia has its faults - the scarce rear passenger leg room is something the vast majority of automotive journalists who have tested the car agree on. Another thing they agree on, however, is its successful design, which is not only pleasing to the eye but also responsible for a Cd of only 0.27.

Opel Insignia OPC Unlimited, 1 of 4Opel Insignia OPC Unlimited, 2 of 4Opel Insignia OPC Unlimited, 3 of 4Opel Insignia OPC Unlimited, 4 of 4

4. BMW E90 3 Series

In our minds, BMW's have never won people over through their aerodynamic design – something which has been the reserved territory of brands, such as Citroen for example. Still, despite the fact that the little bimmer is quite different to look at when compared to the renaissance-like shapes of the Insignia, it has the same Cd value of 0.27 as the Opel. That is, only if it bears a 318i/320i badge  – the reason is that larger wheels and fatter tires, as well as a few other exterior tweaks, increase the Cd number slightly in the name of better stability and driving security.

BMW 3 Series, 1 of 34BMW 3 Series, 2 of 34BMW 3 Series, 3 of 34BMW 3 Series, 4 of 34BMW 3 Series, 5 of 34BMW 3 Series, 6 of 34BMW 3 Series, 7 of 34BMW 3 Series, 8 of 34

1-3. Japanese Wedges versus the Three-Pointed Star: A Three-Way Tie!

There are three cars, which occupy the top of this ranking: the Mercedes-Benz E-Class, the Toyota Prius, and the Honda Insight. They all share a drag coefficient of just 0.25 and two of them – the Prius and the Insight – also share a largely similar design concept. In fact, to use the word ‘share' would not be entirely correct because the Insight came in 2008 in response to the Prius' considerable market success and stole its silhouette in an attempt to steal its sales. Nowadays, however, we are all quite used to automotive anonymity and other such examples abound, so it is hardly scandalous. While the two cars have the same Cd value, the Honda needs it a bit more to compensate for the smaller gasoline engine it packs (1.5 vs. 1.8 liters).

Unlike the above two cars, whose hybrid nature and green marketing obligations force them to be as aerodynamic as possible, the E-Class Mercedes is built around the idea of comfort and luxury. It is the most prestigious and expensive car in this ranking and has the most conventional visual profile of the lot. Therefore, we consider it a small miracle that it manages to equal the achievement of the Japanese ‘eco-wedges'. Hat tip to Mercedes, therefore, as they have found a way to win in one more category without giving up any of their traditional qualities!

Mercedes-Benz E-Class, 1 of 36Mercedes-Benz E-Class, 2 of 36Mercedes-Benz E-Class, 3 of 36Mercedes-Benz E-Class, 4 of 36Mercedes-Benz E-Class, 5 of 36Mercedes-Benz E-Class, 6 of 36Mercedes-Benz E-Class, 7 of 36Mercedes-Benz E-Class, 8 of 36

2011 Toyota Prius v, 1 of 732011 Toyota Prius v, 2 of 732011 Toyota Prius v, 3 of 732011 Toyota Prius v, 4 of 732011 Toyota Prius v, 5 of 732011 Toyota Prius v, 6 of 732011 Toyota Prius v, 7 of 732011 Toyota Prius v, 8 of 73

2011 Honda Insight hybrid, 1 of 32011 Honda Insight hybrid, 2 of 32011 Honda Insight hybrid, 3 of 3