Yep, transmission fluid has a fraction of the detergents that motor oil does. It won't hurt anything being in the sump for a few minutes, but it's a waste of $.
Hi Gents Did a search but found nothing much, so sincere apologies if this is 'old ground'. Engine oil, pre change flush chemicals such as, https://products.liqui-moly.com/engine-flush-plus-3.html, for example. They use words and phrases like 'removes troublesome deposits', 'sludge' and...
As others have stated ATF is not a proper flush and has little detergency:
Originally Posted by Danr42
I've been told by old mechanics to add a quart of ATF 10-15 miles before an oil change. I've done it to flush engines before with relatively new oil still light brown and after 10 miles with ATF it is black.
Originally Posted by MolaKule
I guess some people don't read other threads on this topic but here goes (Ron Ananian not withstanding): First of all, I think we can agree that ATF is a "thin" fluid. Thin fluids are better able to flush dirt and sludge. In addition back then, ATF's had high values of detergency, and in many cases, more than motor oils. BTW, detergencyÂ does not meanÂ it has to have high calcium, sodium, magnesium or whatever values. Detergency can mean it has solvency from other compounds. For example, Pennzoil uses PEG's for dirt and sludge precursor solvency. In the earlier days, ATF's such as Type A had a percentage of Naphthenic base oil, with a bit of sperm whale oil (a naturally occuring ester used for friction modification) and mostly mineral oil. Now both Naphthenic base oils and the sperm whale oils have solvent action. Today, motor oils have more detergency than ATF's, because ATF's are mostly non-polar GroupIII and PAO, with a smidgeon of "not-so-solvent" POE's. About the only detergent/dispersant one sees today in ATF's are the multi-functional calcium additives at about 150 ppm, which is 20 times lower than what you see in motor oils. Those multi-functional calcium additives also act as rust preventers. In addition, most ATF's have only about 300 PPM of phos AW additives. Engine oils have about 2.5 times that amount. My advice is if you have an indication of sludging, use something like ProTec or Rislone Engine Treatment and use it as a FLUSH.Â A FLUSH is a batch of solvent chemicals added to the oil such that the engine is brought up to operating temperature at idle and then the whole schmear is thoroughly drained, with new oil and filter added afterwords. Do not drive with a Flush.