Is oil less dense than water?
Oil is less dense than water. That is why oil floats on water.
Assuming you mean the usual sort of "oil", there is nothing that is both less dense than oil and more dense than water. You have effectively asked the buoyancy equivalent of "what number is bigger than 3 but smaller than 2". Oil is less dense than water so nothing can float in oil but sink in water. If it floats in oil it would have to be less dense than oil so therefore, it will…
Crude oil is less dense than water. This is apparent after oil tanker accidents where the oil floats on the surface of the ocean. http://img.timeinc.net/time/photoessays/2007/skorea_spill/skorea_spill_01.jpg In fact, most oil is less dense than water (ever seen salad dressing that's separated? It's split into it's oil and water components!)