Short answer
GC-LB is a performance designation for automotive service greases defined in ASTM D4950 and certified through NLGI. “LB” is the chassis category and “GC” the wheel bearing category; a GC-LB grease meets the requirements for both. NLGI added a separate High Performance Multiuse (HPM) certification in 2020 for greases that meet tougher requirements.
The ASTM D4950 categories
ASTM D4950 classifies automotive service greases into chassis categories, starting with the letter L, and wheel bearing categories, starting with G. LA and LB are the chassis categories, with LB intended for more severe duty such as heavy loads, vibration and water exposure. GA, GB and GC are the wheel bearing categories, with GC covering mild to severe duty, including the high temperatures found near disc brakes.
Most automotive multipurpose greases on the market are positioned as GC-LB, because that combination covers both chassis points and wheel bearings with one product.
What the tests check
The two categories each have a test table. NLGI’s published summaries list, among other items, a worked penetration range, a minimum dropping point of 150 °C for LB and 220 °C for GC, water washout limits, oil separation, four-ball wear and extreme-pressure tests, corrosion protection and, for GC, a high-temperature bearing life test. LB also includes a fretting wear test aimed at oscillating chassis joints.
Because the ASTM standard is revised from time to time, NLGI points readers to the current edition of ASTM D4950 for exact limits.
The NLGI certification mark
A grease can only display the NLGI certification mark for GC-LB if its marketer has submitted data and been licensed through NLGI’s program. A product description that says “meets GC-LB requirements” without the mark is a supplier statement rather than a certification, so check the current product data and the NLGI listing when certification matters to you.
NLGI HPM and its subcategories
NLGI launched the High Performance Multiuse (HPM) grease certification in December 2020, administered with the Center for Quality Assurance. A grease must meet the HPM core specification first, then can add subcategories for water resistance (WR), high load carrying (HL), salt-water corrosion resistance (CR) and low-temperature performance (LT).
HPM was designed to sit alongside GC-LB rather than replace it overnight. An equipment maker or fleet that specifies HPM, or a particular subcategory, is asking for more than GC-LB alone.
Frequently asked questions
Can I use GC-LB grease in wheel bearings?
GC is the wheel bearing category, so GC-LB greases are intended for both chassis and wheel bearing service. Still follow the vehicle maker’s grease specification and repack procedure.
What is the difference between GC-LB and HPM?
GC-LB is the long-standing ASTM D4950 automotive category. HPM is a newer NLGI certification with a core specification and optional subcategories such as water resistance and high load.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].