Goodmorning,
500km is what they advised voor the cleaning. You may drive it for a longer time. So 1000km is also ok. And due the use of mtc as additive or polytron motor oil the cleaning continues during the use of the product. But the manufacturer says that 500km is actually enough to start using polytron mtc.
In some cases with bad maintenance we noticed that especially with diesel engines a lot of contamination will come lose with the old oil.
Also there is a change that with “clean” oil in combination with MTC the oil becomes dark after a short time. This is not a problem with the polytron mtc, but the cleaning i.c.m with contamination inside the engine causes this.
Hope this help.
Regards,
Kees