I have learned much form the other guys on this board. But I will buy only ACEA A3 oil for my E46 (ie Mobil 1 0w-40). In regard to the properties and disintegration of the oil, I do not think the filter will make any difference stopping the oil from turning to sludge over time. But others are better qualified than me to confirm this. Cheap filter will mean problems, but you need the right oil, and all oils filters will collect inpurties to various degrees.