NLGI Grades and Castrol Spheerol: Choosing the Right Grease

Grease selection goes wrong more often than oil selection, usually because people match the NLGI number and stop there. The number is only one of three things that matter.

What NLGI actually measures

The NLGI grade describes consistency, or how stiff the grease is. NLGI 2 is roughly the texture of smooth peanut butter and covers most general bearing applications. NLGI 1 is softer and suits centralised systems that have to pump grease along a line. NLGI 0 and 00 are softer again, used in some gearboxes and long distribution systems.

Consistency is not load capacity and it is not temperature range. A stiffer grease is not a stronger grease.

Thickener type is the bigger decision

Most general purpose greases use a lithium or lithium complex thickener. Calcium sulphonate greases handle water and corrosion better. Polyurea is common in sealed electric motor bearings. These are not freely interchangeable, and mixing incompatible thickeners can cause the grease to soften and run out of the bearing.

If you are switching thickener type, purge the bearing thoroughly rather than topping up over the old product.

Base oil viscosity

The third factor is the viscosity of the oil held within the thickener. Slow, heavily loaded bearings generally want a heavier base oil; high speed bearings want a lighter one. Two NLGI 2 greases can behave completely differently because of this.

The Castrol ranges

Spheerol covers general industrial and automotive greases, from everyday EP products to bearing and chassis applications. Where loads are severe or the application involves open gears, Molub-Alloy is the heavier duty range. For food production, only the H1 registered Optileb products are appropriate.

Tell us the bearing, the speed, the temperature and whether water is present, and we will narrow it down. We stock the Castrol range in cartridges through to drums. Ask for a quote.