However, limits are posted and enforced in areas that are urbanised, accident-prone or stretches that are under construction.
On some parts with no speed restrictions, 130 kph (81 mph) is recommended, but it is clear that driving faster is not illegal and more than 400 kilometers (248 miles) of German motorways were a great opportunity to find out.
So there are plenty of videos uploaded to YouTube where drivers have posted their speed tests on this public road. One of the latest clips in this category shows a speed test with a Porsche Panamera 4S. You can see the driver of this car pushing the accelerator pedal up to 298 kph (185 mph).
The car in question is a Panamera 4S Diesel, powered by a diesel V8 with 422 horcepower and a maximum torque of 850 Nm (626 lb-ft). It’s paired to an eight-speed PDK automatic gearbox and all-wheel-drive. As a result, the Panamera increases speed at an incredible pace, but without breaking a sweat. At the time of launch (2017) the Panamera 4S Diesel was the fastest diesel-powered production vehicle in the world.
The second generation Panamera is based on the VW Group's new MSB platform. Porsche engineers developed the MSB architecture using a lot of aluminium in its construction. The same metal is used for the doors, hood, roof and tailgate frame. MSB has been the basis for models such as the Bentley GT and GTC, as well as the Flying Spur's replacement.