ディンプル加工

面白いネタ見つけましたよ。
車にゴルフボールの様にディンプル加工したら燃費が良くなるかって話です。

Mythbusters test golf ball-like dimpling effect on fuel economy (*Spoiler Alert!*)

The show's team completely covered a last-gen Ford Taurus with modelers clay and figured out that it would achieve about 26 mpg at a constant 65 mph. They then went about adding over 1,000 dimples to the car's exterior. To keep the experiment consistent, all 1,082 dimples removed from the clay exterior were put in a box and set in the back seat so that the car would weigh exactly the same as before dimpling. The theory is that, like a golf ball, the dimples would reduce the car's drag through the air, thus allowing it to travel the same distance at the same speed using less fuel. The result? Over 29 mpg.

車に粘土貼り付けて、平均104.6km/hの燃費が 11.05km/l だったのに対して、1,000個以上のディンプル付けて、同じように計測したら 12.32km/l になったって事みたいですよ。
空力が良くなって燃費向上したようですね。
リンク先のビデオを見ると詳細が分かりますよ。