I recall reading some of my Grandad's Mechanix Illustrated mags, and the advertisements for oil filters that contained a block of "additives" that repleted the addtives in the oil as your driving stripped them from the oil. It made me wonder. * How did the filter manufacturer know what was needed for all engines, and oil combinations ? * Is there some sort of equilibrium state between solid and soluble additives ? * Given the V.W. specs that change regularly, should they have such a store of "holiday fishfood" in their engine specific oil filters that keeps the additives exactly where the should be for long life ?