Use of ATF to clean engine

["Jevon B. Dade" <jdade@usibr01.usi.edu>]

I am planning on switching to synthetic oil, and I have read on the list 
that you could add ATF to the old oil and it will act a a detergent. If 
this is true, how much should I add, how long should it be in the engine, 
do you do it just before the change? 

any answers would be greatly appreciated.

TIA

J. Dade
88 90