OK.
I guess we are all not on the same page. What I meant was, if an engine has significant sludge build-up, and mine has BTW, (bought it that way,...what a fool), I fail to see how you can remove a pound of sludge *safely* this way.
All the little bits of diamond-hard carbon will be sent to the sump, then sucked thru the oil-pump rotors which run 10thou clearances and rammed into the oil-filter. This product if it does really work without damaging the engine, *must* change the sludge into a liquid, devoid of any nasty hard-bits.
OTOH, if it is only designed to remove normal residue which forms in engines with routine maint, well, that's another story.
regds Jason