Because oil is less dense than water, it will always float on top of water, creating a surface layer of oil. You might have seen this on streets after a heavy rain—some water puddles will have a coating of oil floating on them.

Does synthetic oil float on water?

Most oils are lighter in weight than water. Oil floats on water because it has less density than water. Some of the oils are heavier than water. It will sink to the bottom.

Does heavy oil float on water?

Water molecules are only attracted to water molecules. Oil molecules are only attracted to other oil molecules. Water is more dense (heavier) than oil so they can't mix. Oil floats above the water.