Bearings need grease for one reason only, to reduce friction. As long as the lubricant is performing that service well, there should be no need to change it, or add more. ... Monitor, measure and trend friction levels with ultrasound to know when it is the right time to grease.

Do all bearings have grease?

FOR STARTERS, note that most sealed bearings come pre-greased from the factory with a 25%-35% grease fill. ... However, this effectively destroys the seal's ability to keep contaminants out of the grease; and too much grease “churns” inside the bearing, generating resistance and leading to rapid heat build-up.

What happens if you don't grease bearings?

The inside of the bearing race of the wheel hub was likewise HOT, dry and had metal stuck to it. THAT'S what happens if you don't grease the wheel bearings. They run dry, get hot, literally weld their parts to the hub and spindle, and the wheel falls off.