There is one sure way of removing oil or grease from metal, I have never found it to ever fail. Though you must be extremely careful using it because in high concentrations it can produce serious Caustic burns extremely quickly.
The use of a very strong warm solution of Sodium Hydroxide more commonly named Caustic soda, this is not to be confused with Sodium Carbonate common name Washing Soda. This Caustic Soda mixture saponifies oil and grease that can sometimes be difficult to remove using Alcohol or Petroleum spirits from metals.
