3000 miles ago I decided to go full synthetic with Mobil 1, I prefer to use Amsoil but it is not available in my area only through mail order. My SE has or had at that time 63000 miles and the conventional oil and filter was changed every 3000 miles. I first used Motor Flush with a new cheap filter then replaced the filter with a Wix and Mobil 1 synthetic, 3000 miles later I changed the filter only and added 3/4 qt of Mobil 1. The question is the oil which was in the old filter was dark? will it begin to lighten as time goes on? does it mean that the synthetic is still cleaning whatever crap was left from the last time I changed it?