ATR recommends the use of S4601 synthetic vacuum pump oil in your rotary vane pumps. Unlike mineral based oils, synthetic vacuum pump oil actually cleans your pump as you use it. Because synthetic vacuum pump oil is inert, it suspends contaminants that chemically alter mineral based oils. S4601 synthetic oil contains added oxidizers that will neutralize corrosive contaminants. This helps to extend the pump's useful life as a result of superior vapor pressure characteristics, higher thermal stability, and greater resistance to water. S4601 has a translucent blue color. Color changes in the oil alert the user when the oil needs to be replaced. Additional chemical traps are often not required when synthetic oil is used.