Physical contaminants could include metal shavings, sawdust, or dirt. Chemical contaminants could include solvents, halogens, or saltwater. Metalworking fluids and oils. Industrial hydraulic fluid. Electrical insulating oil.
Industrial process oils.
Oils used as buoyants. This list does not include all types of used oil. Products such as antifreeze and kerosene. Vegetable and animal oil, even when used as a lubricant. Petroleum distillates used as solvents.