Erwin hat geschrieben:does the car have 2 thermostates (as sebastian said), an "oil thermostate" and a "water thermostate"??
Yes, every PLUS has two thermostates, one for the water-cycle and another one for the oil-cycle. If you are starting your cold engine, you are using only the small water-cycle and the small oil-cycle. If the engine gets warmer both thermostates are switching to the big cycles.
If for example the oil-thermostate doesn't work, it could be open all the time or it could be closed all the time. If it is open all time, you need very long, to get a warm engine, but after a time it would become warm. If it is closed, you will get very fast a to hot engine!