You can easily tell it's the Autobahn when this SUV's owner is taking a "relaxed drive home" while effortlessly doing 126 mph (203 km/h)… The man driving a current-generation BMW X5 M50d had a change of heart after noticing an original Audi A7 Sportback going at full tilt, deciding to spice up his commute by flooring it as well.

The BMW's inline-six 3.0-litre diesel engine put its four turbochargers to work in an attempt to catch the sleek Sportback on an unrestricted section of Germany's glorious motorway. The X5 M50d got up to 161 mph (260 km/h) but then the pesky electronic top speed limiter kicked in and prevented the Bimmer from going faster. In reality, the high-performance diesel SUV was likely doing 155 mph (250 km/h) since that's when the limiter is programmed to do its thing.

The Audi A7 driver was kind enough to switch lanes and make room for the X5, but the diesel behemoth simply wasn't able to overtake the Sportback. The two high-end vehicles had just about the same speed for a while until the Audi slowed down to prepare to exit the Autobahn, but not before giving the BMW driver a thumbs up for the high-speed chase.

That version of the X5 is a dying breed as BMW is phasing out the complex engine codenamed "B57" with its pair of low-pressure turbos and another pair of high-pressure turbos. The 400-bhp mill produces a whopping 561 pound-feet (760 Newton-metres) of torque and helps the luxobarge hit 62 mph (100 km/h) from a standstill in just 5.2 seconds.

The acceleration is not too shabby considering the luxury SUV weighs about as much as the moon, tipping the scales at 2,275 kilograms (5,015 pounds). BMW used this engine in the "M50d" versions of the X5, X6, and X7 as well as in the 750d – all of which had xDrive and an automatic transmission.