bridggar:

How can turning off stop\start be like tuning? You can manually override the crappy system so what's the difference? It's a configuration preference - like not unlocking all doors.

I didn’t write the laws and I am no lawyer.

You are not allowed to change the original electronic of the car in Germany.

Example: in the late 90ies I had a car with one of the first (?) automatic systems to switch on the light when it is getting dark. It doesn’t work very well, when it became foggy or in winter when we had snow the system didn’t switch on the lights as early as I wanted. I changed the electronics (don’t ask me how) to the Swedish model where the light is always on when you start the engine. You probably know that in Germany every car has to visit the TUEV to get a certificate “road legal for the next 2 years”. I didn’t get this certificate because of my modification (although you are allowed to drive with the lights on). I had to reconfigure the car, visit the TUEV for a second time, had to pay the fees (all? I can’t remember) for a second time and then I got the mandatory certificate.

And start/stop automatic is probably even worse because by that you change the fuel consumption which is important for the tax calculation as RC mentioned

So if your car is modified in that way it isn’t road legal. Theoretically you can even have trouble with your insurance if you are involved in a crash (never heard of it)