This is always an interesting myth. Now maybe there is an oil pan out there without such deep inset threads, but I have not come across that in my short life so far. The FAQs on Fumoto provide a few pictures.Did this thought ever cross your mind that using the Fumoto valve that you aren't draining all of the oil from the bottom of the oil pan?
Every car would be different. However, I checked this on the last oil change for my 2011 Kia Optima. I drained the oil through the fumoto valve and let it drain for 30 minutes like I always do. I then removed the valve so that I could use it on my new Kia K5 when it came in. When I removed the valve there were three table spoons of oil (about 20 ml) after a further 15 minutes of draining. So I would suggest this is not an issue.Did this thought ever cross your mind that using the Fumoto valve that you aren't draining all of the oil from the bottom of the oil pan?