Where u know that density of water and oil differs using this phenomenon we can separate the oil from water
Take funnel shaped type equipment that has tap as stopcock at the bottom , and drain out the water with it from untill the oil left out .
Another techniques is Pour all the water and oil into a clear plastic bottle . You can have whatever size bottle you need as long as it has a sealable cap with a tap or make a hole in the cap insert a straw and clip it's end so that no leaking. Close the bottle as tightly and keep it for a time with out disturbing it .after this u will find out both water and oil will be separated ..where oil stay's on top of water so you can drain the water easily