Nothing sinister or otherwise
Using the flush shouldn’t be needed if doing regular changes and using quality oil.
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That's what I have always thought, but Penrite recommends it each time so I am confused. Like most on here I change the oil each 12,000km or so. I flushed for the first time when I changed over to Penrite at about 50,000km and again at the last change at 104,000km. So I'm having an each way bet, I suppose!