Glossary Term
Definition and Purpose
The lubricating fluid in a grease can be a mineral oil (derived from petroleum), a synthetic fluid, or a vegetable-based fluid. Lubricant base fluids are divided into five groups defined by the American Petroleum Institute (API) as follows: Group I – Paraffinic mineral oil, typically produced from petroleum by solvent extraction processes, with a sulfur content of >0.03% and/or saturates <90%. The viscosity index (VI) ranges from 80 to 120. Group II – Paraffinic mineral oil, typically produced from petroleum by a combination of solvent extraction and catalytic processes, with a sulfur content of <0.03% and saturates >90%. The viscosity index is in the range from 80 to 120.