my engine oil seems dark after 7000km interval and after changing oil it still seems to be dark considered the oil is fresh. what could be the issue and any advice what i should do? engine runs fine and no power loss etc.....
I wouldn't worry about the oil color too much if the car is running fine, its just that some residue is left from the old oil hence the dark color. Happened to me too and changed the oil again on the same day and it's all clear and looking fresh.
Smelling the oil could also help, try dipping in a few times and see if it has any unusual smokey smell or something. To see fresh looking oil basically change the oil for a second time.
Usually not all the oil is drained in a change... there is a fair bit left in the oil coolers, oil lines & a little in the sump. If you want to flush it a bit more try using the same spec but cheaper brand of oil to flush and run the engine in for a few miles & then empty and put your usual oil in.
In rx7/rx8s this was a favourable method since mineral oil is super cheap!
As already said, the colour of the oil is not an indication of its condition. Turbocharged cars seem to blacken oil faster than anything. I think it's better to just change oil without flushing as long as you obey the intervals.
Far better to mix new oil with slightly older oil of the same spec, instead of mixing it with the cheapest oil available (flushing oil). If you really want it super clean in colour, flush it with the same grade oil the car runs on.