Yes, definitely I understand why it goes black
The engine was very dirty and the oil was very very black when I bought it,
so I changed the oil twice in one day, just for cleanning the engine.
it still was very black after it was drained first time, even only run about 150kms,
then I put the helix and after hundreds kms it seems alright, now has it has done 2000kms,
just want to make the engine more cleanning.
other hand, I like to do the major service frequently,
it makes me very raughty after the engine oil and filter replaced everytime, just like give myself a sauna
so that's why I'd like to change the oil again in such a short period.