DLE-POLYOLESTER FROM RACING OIL In Nürburgring

 The MB- 229.51 is a specification for Diesel cars with after-treatment requirements like Diesel particle Filter. Not really relevant for Racing, right?

Basically, yes, you could use such a product also for racing. The higher the viscosity the better as this better protects from wear under such tough racing circumstances.

 However, we use a special racing oil for such kind of races as these cars never go on the normal street and are serviced during and before/after the race.

The additive balance is somewhat different as you do not have to care too much about certain characteristics but need to focus on others. So in case you want to use any of the 3 above(5W/40 C3.5W/50 C3.5W/60 C3), I would rather go with the 60 visco.