Dont worry about the oil/water thing - even if they ask you to show them where it is and you dont know, its only 1 minor I *think*

You never know, if you feel you dont think you're going to pass you might relax more and not mess up by trying to do everything too perfect - when i passed my test I thought I'd failed from the beginning so didnt care after that, and passed

Good luck with it though hun!!

x