Lubrication is the key for good bearing behaviour under rotating speed and loads. Bearings can be lubricated by oil or grease. SKF also has gained a very large knowledge on lubricants. Hence SKF is able to recommend the best lubricant for specific applications. SKF still performs quite some research on this subject.

How does a lubricant work?
If lubricated correctly, a very thin film of oil separates the balls and raceways and cage. This also ensures very low friction in the bearing. When a bearing has insufficient lubrication, the oil film is too thin and balls and rings are in direct contact, which generates friction and heat in the bearing. This heat gives rise to dilatation and increase of the ball diameter; the risk exists that the bearing internal clearance becomes too small with blockage of the bearing as a result.

Oil
There are mineral, vegetal and synthetic oils. Important characteristics are i.e. viscosity, corrosion resistance, etc. The selection depends on operating conditions.For speed skating SKF recommends oil lubrication because it brings far better rolling. However using oiled-bearings means the necessity to lubricate regularly, therefore oil is supplied with the bearings.

Grease
As a standard for inline roller-skating and skateboarding SKF recommends grease-lubricated bearings. SKF bearings can be supplied with different types of grease depending on the application. For good skating SKF recommends LGLT2 grease.
SKF LGLT 2 ensures maintenance free bearings, however following needs to be considered:

Grease use time limit: All greases are bleeding their basic oil. When this oil is gone there is only soap left, which is drying quickly. The soap is like black cement when sticking on balls and raceways. This can block the bearing. Approximately one year is enough to dry the grease.
Dust and dirt: Dust or dirt particles that enter the grease create contamination, which destroys the lubrication capacities of the grease. There is need to change the grease as soon as possible!
Water: Water mixed with grease produces "mayonnaise" which is far from being a good lubricant. This keeps the water in the bearing which quickly generates rust when the bearing is at standstill.