Choosing the right grease: NLGI, thickener types and mixing
Grease is essentially oil held in place by a thickener. Choosing the right one means knowing three things: consistency, thickener type and operating conditions.
NLGI: consistency
The NLGI number shows how stiff a grease is, from 000 (almost fluid) to 6 (very hard). NLGI 2 is the most common grade and suits most bearings, chassis points and joints. Softer greases (0 and 1) are used in centralised lubrication systems and cold weather.
Thickener type
- Lithium: multipurpose and economical, for wheel bearings, chassis points and electric motors.
- Lithium complex: a higher dropping point and more heat tolerance; for disc-brake hubs, kilns and steel mills.
- Calcium: excellent water resistance; for agriculture, marine and washdown equipment.
- Moly (molybdenum disulphide): for pins, bushes and joints under shock loads.
The base oil matters too
The base oil viscosity should match the component’s speed and load: high speeds call for a thinner base oil, heavy loads at low speed for a thicker one.
Mixing greases
Not all greases are compatible. Mixing some thickeners (for example lithium with certain polyurea or bentonite greases) can make the grease soften and run out. When switching type, purge as much old grease as possible and shorten the regreasing interval at first.
A common mistake: too much grease
Packing a bearing completely full causes overheating and seal damage. Filling one third to one half of the free space is usually enough; get the exact quantity and interval from the equipment maker.
Quick answers
What does NLGI 2 mean?
Can two greases be mixed?
Which grease is best for high temperatures?
See our greases range, or ask our sales team for a recommendation and price.
