From Longman Dictionary of Contemporary Englishnot mixnot mixMIXif two different ideas, activities etc do not mix, there are problems when they are combined Smoking and babies don’t mix. → mix
Examples from the Corpus
not mix• Safety and alcohol do not mix.• Again the same point emerges: high social standing and systematic training did not mix.• It is not the first time that Chamonix officials have decided youth and mountains do not mix.• Note that you can not mix endorsement marks, ie. you can not accept some and reject others at the same time.• Mrs Flaherty and the nans did not mix in the same circles.• If proof was needed that soccer and the City do not mix, this messy situation is it.• Sink mixers have divided flow so that the hot and cold water do not mix until they have left the tap.• The behavioural patterns are so different that they do not mix well.• Ideally this water should be wrung out into another container and not mixed with fresh rinse water. 