Just remember one thing...scale effect. Applying a liquid that is 1:1 to represent something that is in scale a fraction of the depth might make it look very unrealistic once applied.
Oil is typically displayed in modeling as nothing more than a stain to give the illusion of liquid.
You might find that you have a puddle that is a foot deep in scale versus the 1/4 inch it really would be in actual depth. Convert that 1/4 inch down to 1:35, 1:48 or 1:72 scale and you have in essence something that can't actually be replicated accurately, so we opt to use a stain instead of the pool of liquid.