A bunch of ATF makes me nervous, it does have a bunch of detergents but as mentioned it’s not a great lubricant.
On sludgey engines I run a quart of marvel mystery oil and cheap oil for the first 3 oil changes. Change about 500-1000 miles. Then I put a half quart in about 500 miles before a regularly scheduled oil change. It does a good job getting the junk out, unsticking lifters and it’s proven safe to use in an engine.
We have a 300k mile Toyota at work that sat for 15 years. I now get normal looking dirty oil at the 3000 mile interval. It looked like diesel oil and clattered for awhile.