Roughly a third of premature bearing failures are lubrication-related. Grease lubrication is simplest and seals well; choose grease by NLGI consistency (No. 2 or 3), dropping point at least 20–30℃ above operating temperature, base-oil viscosity matched to speed and load, and thickener type. Fill 30–50% of the free internal space — overfilling causes churning heat. Oil lubrication (oil bath, jet or oil-air) suits high speed and heat, cooling as well as lubricating. Regular relubrication intervals, cleaning out old grease, and condition-based top-ups complete the guide.