[Clifford Pope]

I used to believe in these flushing agents, until I read the view that in dislodging hardened gunk and letting it circulate they actually did more harm than good. So I don't now know whether I have reached 310,000 miles because of flushing, or despite it!
I now think that the important thing is a regular oil and filter change after a long run, and that flushing is unneccessary.
The only time I would now use it would be on taking over a very dirty and neglected engine. I then use a charge of flusher, drain, fill with cheap oil, run for about 100 miles, than drain, and finally refill with a good oil.