Vacuum Pump Oil & Grease

Follow the pump manual: viscosity grade is matched to the pump's clearances and speed, and using a thinner or thicker oil costs you ultimate pressure or shaft power. Direct-drive rotary vane pumps generally take a lighter grade than belt-driven ones. If you have lost the manual, send the pump model.

Mineral oil is the cheapest and fine for clean air. Synthetic (PAO, ester) resists oxidation and higher temperature and lasts longer. PFPE (perfluoropolyether) is chemically inert and non-flammable — it is what you use with oxygen service or aggressive process gases, at many times the price.

Do not mix chemistries — mineral with PFPE in particular can form a gel and seize the pump. Mixing brands within the same chemistry and grade is tolerable when topping up, but at a full change drain, flush and refill with one product.

As hazardous waste through a licensed handler — used vacuum oil carries whatever the process put into it, which can include solvents, acids or particulates. Oil from a semiconductor or chemical process should never go into a general waste-oil drum without checking what is in it.