Regardless of the reason, you'll have completely fresh oil in the engine only one day of the life of the vehicle - the day you bought it. My personal opinion is that this is a poor design.
Most modern vehicles won't drain completely unless you play a little game with them. Boys and girls, try this at home:
- Pull the plug on the crankcase and let the oil drain completely.
- Replace the crankcase drain plug.
- Pull the oil filter and let that also drain completely.
- Now pull the crankcase drain plug and see how much MORE oil drains out.
It's an extra step, but it's well worth it to not immediately contaminate your oil after spending upwards of $50 on oil and filter and an hour+ of your time.
If you can't completely drain an engine of dirty motor oil, it's evidence of poor design. They could put a drain on the oil cooler. They could resolve the issue in the design phase. They didn't. Bad engineering.