TOTAL DRAIN
For years pilots and mechanics have tried to drain ALL the oil out of their engines at oil change.
Oil changes are necessary; the question is how to get out all the dirty oil. Much to the dismay of the pilot, the new oil becomes dirty after the engine is started. Almost as dirty as the old oil. The reason is too much oil and contaminants remaining in the oil sump after all possible oil is drained.
Most Continental 470, 520 and 550 engines have almost a quart of the dirtiest oil in the bottom of the sump after draining. This is where the heaviest contaminants go after engine shut down. Interesting enough, that is also where the oil pick-up tube is. These contaminants and dirty oil are the first to be sucked up into the oil pump and distributed through the main bearings after engine start up.
Texas Skyways, Inc. now has approval to install a drain plug in the lowest point of the oil sump. The 'TOTAL DRAIN™' plug can be mounted to point straight down or at an angle to point forward or to either side for convenient draining.
The good news is the contaminants drain first. The sump can even be flushed if you like. Everything drains out.

Photo By Scott Slocum