Certified Lubrication Specialist Practice Test

NLGI 2 is the standard grease grade for bearing applications because it strikes a practical balance between staying power and workability. This grade has a moderate thickness that allows the grease to form a protective lubricating film on bearing surfaces while still being easy to pump or apply into the bearing housing. If the grease is too fluid (lower grades), it won’t stay in place and can squeeze out under load or at high speeds, leading to insufficient lubrication. If it’s too stiff (higher grades), it’s hard to pump, can hinder entry into tight clearances, and may increase starting torque or cause uneven lubrication. NLGI 2 works well for a wide range of bearing speeds and loads, making it the common choice in many industrial and automotive bearings.