"A couple notable cautions:
Mark Drillock [8/20/2013]
I don't fully support doing the M Port after learning of 2 people who suffered burned up dash wiring when the motor later seized. Both cases involved motors that were pretty frozen up before the lubrication and worked for a while after the lubrication, but could have resulted in the complete loss of the vehicles to fire. Not worth it.

David Beierl [6/14/2016]
I recently took my heater box out after several years of spraying oil through the "Mullendore port" to stop the bearing squeaking -- the oil had made a nasty mess of the commutator, so the more precise your aim the better. Regardless, it's a band-aid."

1) Two people who didn't finish the job or perform it properly. FWIW, when a motor seizes it blows the fuse. Install the wrong/higher-amp fuse? You get what you deserve. :p (the one I fixed lasted, and was 'frozen up' at the start)

2) If you just 'spray oil in a hole' of course it's gonna make a mess.

In case some readers don't know what I actually performed on the original 'port job': I used a penetrant (or 2+2, I don't recall) to dissolve the 'gunk' that had seized the outboard fan bearing, a bronze bearing. When it freed up it was run a little, then reapplication and repeat until it was running 'free as the wind'. THEN Triflow lube (using an extended straw) was applied to the bearing via the exposed end of the shaft which wicked it into the bearing with the fan on low speed. No mess made, no dangerous situation down the road. Perhaps my first response could have been a bit less terse, but hey, come over here and try on my shoes and see how they hurt your feet. LOL!