I drive a 95' F350 PSD Dually and haul a trailer
I used a 1 ounce animal vaccine syringe and windshield wiper hose to fashion a vacuum pump
to remove the oil from the high pressure reservoir
and fill it back up again.
I do this at every oil change.
The PSD injectors require clean oil to
have a useful life, when you buy a used truck
you never know how often the oil was changed.
Dirty oil is the primary cause of premature injector failure.
I change my oil & filter every 5000 miles.
I use Shell Synthetic T3.
Take care of your Ford and it will take care
of you ......