The delivering of lubricant is influenced by many different factors.
One of the most important ones is the penetration (consistency). The higher the penetration NLGI-Class the stiffer the lubricant. Generally spoken: stiffer lubricant (grease) can not be pumped that easily. NLGI-Class 000 is the lowest class, i.e. the softest lubricant, NLGI-Class 6 is the stiffest, viscousest lubricant.
Lubricants up to NLGI-Class 2 can be normally therefore the pumped without any problems.
Most of the used lubricants correspond with the NLGI-Class 2.
NLGI - Class = Rating of the lubricants, which is done by the National Lubricating Grease Institute.
NLGI - Class
Walkpenetration acc. DIN ISO 2137 Unit = 0.10 mm
445 up to 475
400 up to 430
355 up to 385
310 up to 340
265 up to 295
220 up to 250
175 up to 205
130 up to 160
85 up to 115
The apparent dynamical viscosity, which is provided by certain manufacturers of lubricants, has an important meaning. If it goes beyond 5000 m Pa.s, pumping with conventional lubricant pumps or systems is complicated or not even possible.
At the same time the surrounding temperature as well as the length of the conduits or hoses is also important.
Synthetic or Bio-lubricants can affect the seal materials.
If the solid content parts in the lubricant are too big, the pumping of such lubricant can be impossible with a conventional pump.
Do not confuse silicone grease with silicone used for sealing (no lubricant).