[Vman455]

Originally Posted by Phase

Can anyone explain why the new Mercedes EV that gets 1000km of range is 2 points lower in drag than the xl1? Heck the xl1 has a longer boat tail, is narrower, rear wheel spats, and deleted the side mirrors

The Mercedes keeps the side mirrors and doesn’t use rear wheel spats!!

It could be any number of reasons. Even small changes in body shape can have significant effects on airflow, as I've constantly found in testing (and you--and everyone else here--could too). A good example of this is the last section in this article:

To answer that, let’s compare my truck to a friend’s 2011 Toyota Tacoma. Not only is this a truck of similar shape and size, it’s built by the same company, is the successor to my older truck (one generation removed and fattened up for the US market), and may have even been tested in the same wind tunnel when it was designed. How similar are the flows over the side windows of each truck?



Answer: not very. Less disruption from the mirror, less separation at the A-pillar, and less turbulence in general can be seen on the newer truck, tested at the same speed, on the same road, and in similar conditions.

Seemingly inconsequential differences in the shape of each truck’s hood, wheel arches, windshield, A-pillar, roof, door, mirror, and window add up to a substantial difference in the character of the airflow over them. The flow over the side window of the 2011 Tacoma is cleaner with a mirror than the 1991 Hilux without one. Only twenty years separate these two trucks, and to many people they look pretty much the same!

You're welcome to believe the people who will post definitive answers to your question here (as above), but the reality is none of us can say.