i assumed it wouldn't be smart to use any old gunk on more modern diesels.
i have been driving 1.6vw turbo diesels and had a ford 6.9 and have messed with veggie oil and atf and diesel purge.
i used to get the cheap 2 stroke oil or atf and add it to each tank for a bit of lube because i had read diesel formulations had changed and of course read it on some forums
i used it because it was cheaper than diesel kleen at the time at walmart.
i had to save atleast a handfull of these old injection pumps myself that had gunk in them and for whatever reason getting atf fluid through the system straight and letting it sit for a day or two after some initial running cleaned things up way more than diesel purge system in a can?
i brought back 2 vehicles with a bad batch of oil gas that gummed the crap out of their pumps. got them running again. cleaned up some stuff but i still took those injection pumps apart because there were parts like vanes with crust buildup that didn't get totally cleaned out.