Does an NLGI grease grade tell me the base oil viscosity needed by a bearing?

LILY Bearing | 2026-10-28

Best answer

Firmness does not identify the lubricating oil

Grease contains a base oil, a thickener and additives.

Its consistency describes how firm or soft the grease is under the specified test, whereas the base oil has a viscosity that influences lubrication under operating conditions. JTEKT treats those as separate selection properties. Two greases with the same NLGI grade can therefore contain different base oils and have different relevant performance characteristics. Selecting a replacement solely because both products are labelled NLGI 2 loses information rather than establishing equivalence. The bearing, speed, temperature, load and lubrication arrangement still need to be considered alongside the actual lubricant product data.

Compare two greases without confusing the columns

Create one column for consistency and another for base oil viscosity at its stated reference temperature.

In a hypothetical comparison, both products might be NLGI 2 while one lists 100 mm²/s and the other 220 mm²/s at 40°C. Those assumed numbers demonstrate that the consistency match does not settle the viscosity match; they are not product recommendations. Add base oil type, thickener, additives and relevant manufacturer approvals to the comparison. If a supplier provides only the NLGI grade, ask for the missing technical data. Keep the original product identity in the maintenance record so the abbreviated grade does not become the entire lubricant specification.