"Lava lamps": the liquid is a plastic with a very low melting point.
"lighter fluid" and whiskey: lighter fluid is xylene and it does not mix with either ethanol nor water.
Silicon lubricant and milk: silicon oil is similar to ordinary oil. Milk contains emulsifiers to dissolve oil, but I doubt these work with silicon.
Gasoline and grape juice: gasoline is a hydrocarbon and these compounds don't mix with sugar nor water.