What do you think will be the main reason? With the amount of stop and go driving I have done over the years and not really changed the oil more often I thought I would see a bit more discoloration or sludge.
Not sure about 0w-40, but have used Mobil 1 advanced fuel economy exclusively in my 05 Corolla. Had to pull the valve cover last weekend & shocked to see how clean it is @ 200,000 + miles. Oil has been changed annually at up to 12,000 mile intervals. Was wondering if sticking to the same brand...