oil change

One guy used to fire it up and let it pump out. Whatever is in torque was filtered, so it will dilute the new oil with old. Been done for many years. The oil change shops that run the machine for swapping oil do not change the filter,so wasteful. Do fluid change and then dump oil to swap filter over a couple quarts of used oil in torque? If oil is dirty enough to cause concern its likely too late already.
I drop pan,weld in a drain bung,wash pan and replace filter. Reassemble and fill.