It depends who does it and how much of a fuck they give.
Up to 50-600ml can be left behind, and that’s if you give a fuck. Ever hear about people who measure after an oil change at the dealer and they’re over by half a qt? That’s because dude who did the oil change left half a qt of old oil in the pan. And decided to just add 6 and call it a day.
Imagine following vw’s maintenance plan. Changing your oil every 10k miles. Yet carrying a significant overage due to someone not sucking more of it out.
No thanks. Fuck extractors. I remember when they were first rolled into my dealership. Dude who was showing us how to use it sucked as much as possible. Lifted the car. Removed the plug. We measured out about 150-200ml.
Nope. Extractor oil changes should be cheaper considering the job isn’t being done right.
I've seen it at 100-150ml left behind. I've tried putting in about half quart back in and extract it out. You'll see the dirty oil come out...then it'll be clear. I'm willing to be that in the long term...that bit of left over oil will make zero difference in engine wear.