i clean my bb4 pump at the end of the year, or if i suck some sap up, with diesel. i usually let it run for half an hour or so, then drain and fill back up with oil. On the subject of oil turning yellow/white... i bought a large container of pump oil last season that would be clear when cold, then once the pump would run, would turn cloudy for the first 20-30 minutes, then would be crystal clear. can't recall the brand, but i was told it was normal for some oils? not 100% sure if that's correct, but my pump preformed normal with it. for what it's worth...