I recently bought a new suitcase which is one of the hard plastic case types. There was a sticky peel off label on the outside of it. On removing this it has left a sticky mark that will only collect dirt etc. I've tried warm soapy water to clean it with no success. I don't want to try nail polish remover or anything caustic like that in case it damages the plastic. Any ideas?
Everyone should have a bottle of 'Sticky Stuff Remover', which is made for the job. (See Google).
Otherwise, WD40 is pretty good, won't harm your case, and is washed off with warm soapy water.