erk that turned into a long wittering post hope it makes sense to all those that can be arsed to read it
did an experiment with a nasty old v8 heres a quick write up
i flushed a sick 3.5 v8 after putting clean multigrade 20-50 mineral oil in and ran it @ 2000 rpm for 15 mins to get hot, the oil had allready gone really black. added 2 cans of forte engine flush and let it run for another 15 mins for the first 10 mins it smoked LOTS. i then droped the oil then added a few more ltrs and let it come straight out the drain just to push any remaing crud out. then changed the filter and refilled it with 20-50 and let it run for another 15 mins the oil had gone really black again.
on lifting the rocker covers the tops of the heads looked no diffent to the usual dead v8 i then draned the sump again to have a look and practicaly everythign was coverd with heavy deposits. so put it back together with another filter and filled it with neat ATF and drove it about for 2 days. the engine then developed oil pressure problems. on removal the oil filter was heavy and when sliced open looked inpressivly full, witht the sump off it looked a bit cleaner but the pickup was blocked, on the plus side the engine was running quiter before it developed oil pressure probelms but under the rocker covers looked diffrent.
engine was then removed and the 4.2 that had been sitting there all allong was fitted
my conclusions are as follows
so my opinion is oil flushes are not that effective ( and expensive ) you may as well flush with clean oil and just change it more often, 5ltrs of oil + a £10 flush every 10k or 5 ltrs of oil every 5K = same cost i'll go with the oil
as for the ATF it's a high detergent clean oil and imo works better than any of the flushes and faster than clean enigne oil tho wouldn't recomend putting more than 1ltr of it in your enigne oil. ATF flushing is good for solveng problems comeing from internal oilways like loud tappets. but it dosent work miracles. if an engine is internaly coverd in thick layers of backed on gunk ( rover v8's favoret trick ) theer is no practical way to shift it other than takeing it apart. ATF will shift some of it but the sheer volume of gunk in some engine may overcome the filters makeing it a kill or cure
where there is a good strong flow of hot oil the detergents in ATF will move gunk internaly so for oil ways and tappets ect it's a good thing. but i would not recomend useing it as a preventaive measure regular oil changes are for that. as fresh oil will clean oilways as well.
for enignes that are completly caked is thick black gunk are pritty much doomed
8 and 16v engines thankfully don't actualy suffer horendous levels of gunk ( the breathers can look bad but compared to some engines thats nothing ) if they have good oil pressure but are tappety on the top end ATF is all good as it's unlikey to find quantites of gunk that are going to cause problems for the pickup and filter.
20v's dnt far so well but thats because of the stupid service intervals on longlife motors the first symtom with thes being low pressure due to blocked pickups means flushing is unwise and it's far better to clean out the sump and pickup then oil flush with ATF
