GO WITH THE FLOW

The most aerodynamic car Audi has ever made... is a great big executive barge. And when the smoke clears, you'll see it's been a long time coming...

- OLLIE KEW

ON PAPER, WE WANT OUR CARS TO BE AS AERODYNAMIC AS POSSIBLE.

We want to move about quickly, using no money-sapping energy. We don't want to be disturbed by wind noise either. So why don't conspicuously slippery cars tend to sell? Ask Hyundai how the swoopy Ioniq 6 is doing versus the blocky Ioniq 5.

Mercedes has already admitted fixing wheels to a herd of elephant seals has not lured its traditional customers into the EQ family, so the next set of electric Benzes will go back to having a bonnet, a roofline and a boot instead of the body composition of a garden slug.

There are exceptions, but for every Toyota Prius or Citroen DS success story, there's a Honda Insight, a Chrysler Airflow, an Audi A2. The trick to designing a car the air doesn't notice passing by is that we don't notice that's what it's up to.

I'm paraphrasing what Dr Moni Islam, Audi's chief of aerodynamics, has been explaining from inside his open plan office: the company Windkanal [wind tunnel] in Ingolstadt. Opened in 1999, it's been in operation for a quarter of a century - 15 hours a day, five days a week.

"If you look in a university textbook, you'll see very quickly how to make a car that has a drag coefficient of 0.16 or something," says Moni. "A teardrop, basically that's very easy. But a car that fulfils all kinds of different customer requirements space, safety, cooling, packaging - that's the challenge."

Which brings us neatly to the car being tickled by a smoke trace in front of us: the new A6 e-tron. It looks like an Audi. Even if you prised the badged off, you'd recognise the squared off grille motif and stout shoulders. It's a spacious estate, not a nondescript lozenge. And yet it's the most aerodynamic Audi ever made.