It all sounds like a lot of work, storing the used oil, taking it to the
dump (or having a large holding tank). My mechanic does an oil change with
10 qts and a new filter for around $125.00.

I can buy oil in bulk for around 3.50 a quart, and a filter is around 20.00
(as far as I remember). With his shop helper he can do the change in an
hour, while it takes me around twice as long doing it alone. Add in the
cost, time, and hassle of storing the used oil or going to the dump to get
rid of it, the price may just break even. (Three plus hours of time to do
the job and get rid of the oil may be worth the extra 55.00)

It is three hours that could be spent flying, sleeping, drinking beer, or
doing some other worthwhile activity like helping coach my son's hockey
team, etc.

I still favor the idea of driving down a rural road at night and dribbling
out a little at a time. It helps keep the dust down in summer. (at least
that's what they said when I saw them do it in a grass strip in Vermont,
where I learned to fly).