I used the Amsoil flush
Doc, I used the Amsoil engine flush when I went from Delo 400 to Amsoil 15W-40 HDD&M at 32K miles on my engine. I then went 5K on my first dose of Amsoil, sent in a sample to Blackstone as I have with the Delo since day one, changed the oil and filter, then went another 5K on the next dose of Amsoil, sampled and changed filter, and will next change the Amsoil when it gets a total of 10K on the current dose. As of today, I am on my second dose of Amsoil, with a total of ~12K miles on Amsoil. All oil analysis reports have been great since day one.
Oh, I used 2 cans of the Amsoil engine flush, as per their recommendations. I followed their directions when using it.
Just my personal experience.
Tom