Hmmm and also when draining the engine it's likely that some will remain in the cooler even with a flush so no wiser. It always used to be simple, fill oil when cold to dip mark max, now with modern engines comes check when hot, or check with engine hot but turned off fo 5 minutes or check when running at idle, next it'll be 'we don't know sir we advise you check it whilst you have a finger up your £$£%$$ FFS AAAARRRGGHHHHH LOL