One thing that OLMs do not do is track combustion particles, dust, moisture in the air, and so on; all of which end up in the motor oil.
I would hope that Yoshi rethinks performing oil changes for this person. The owner of that Civic is obviously trying to cheap out and at some point this could easily go south. The Honda dealer here charges 35 bucks for an oil change. Why even bother with anyone else for that price.
It was stated that a dealer cannot refuse engine warranty because of a DIY oil change. That is simply not true. Look at the potential for a future problem in this case; and there are tons of potential cases every day.