Just a curiosity question, assume your injectors and valves are gunked up in your port injected car. Then you start putting in Shell V Power or a bottle of Techron to clean that stuff away. Where does the gunk go after it's washed off?
That's my understanding. While it probably wouldn't degrade the oil much if you ran a bottle of PEA based cleaner early in an oil change ...I like to do it before changing the oil for the reason SC M states.
The reason they recommend doing it before an oil change, and not using it too often, seems to be because of concerns with PEA or its byproducts getting into the crankcase and causing sludge and varnish. Here's a study done by Chevron in 2020 (a lot of it is available by clicking the preview). Two of the three PEA cleaners tested caused excessive varnish within two 10k mile OCIs, with a fuel cleaner treatment every 3,000 miles.