I'll interject here that Dave's experience is one of the few actual
benefits of an engine flush. If you do happen to get something lodged in
a small passage, the flusher could possibly push it out.
If I had a customer with a valve tap, I'd recommend trying an engine flush
prior to engaging in extensive and costly engine repairs. What's to lose?
But it's also important to know that success in these endeavors is mixed.
I've stopped some valve taps with the machine, but others still remained.
I had one car flushed after the owner failed to change the oil and the
delivery passages were restricted. It bought the customer about 6 months
before the bearing clearances were bad enough that the oil pressure was
I don't have a problem with the flusher, particularly. Like most things,
it has a usefulness that cannot be denied. But the issue is that services
like this marketed as some sort of regular maintenance service or some
magic bullet. Well, they aren't. There's no benefit to flushing an
engine crankcase that has no problem.
If your engine is sludged, but you are having no actual oiling issues, the
procedure has no more value than adding 1/2 qt. of ATF with each oil
change, and, like Matt correctly pointed out, the flush can *cause*
problems if pieces of sludge are knocked loose into the oil pan. With no
oiling issues, it'd be far better to try to gradually dissolve the sludge.