One thing to bear in mind is the fact that todate I have yet to find a method of doing a complete drain down,quasimotors recomend changing four times I think,I have done two changes within a week and an improvement was evident,but how many untill you could be sure that you had a full synthetic box full,I shudder to think.Of course if the box was out and dry,then I too would be interested in any differance