ASTM D 4950 includes specifications for two Category Groups: chassis lubricants (letter designation L) and wheel bearing lubricants (letter designation G). Performance Classifications within these Groups result in two letter designations for chassis greases (LA and LB), and three for wheel bearing greases (GA, GB, and GC). The automotive industry is in general agreement that the highest performance classification, to date, in each group (LB and GC) is suitable for service relubrication.

So greases that are able to pass the requirements for NLGI Service GC-LB are probably superior (for wheel bearings) to those that do not pass.