Grease selection is not guesswork, and the "one grease fits all" approach I see in too many plants is responsible for a staggering number of preventable bearing failures. Every grease is fundamentally three components: a base oil (60 to 90 percent by weight) that provides the lubricating film, a thickener (5 to 30 percent) that holds the oil in place and determines structural properties, and an additive package (0 to 10 percent) that provides EP protection, corrosion inhibition, and oxidation resistance. The base oil viscosity is the single most critical parameter — it must be matched to the bearing's speed factor (n x dm, where n is RPM and dm is mean bearing diameter in mm). For a standard 6310 deep groove ball bearing running at 1,450 RPM on a pump, dm equals 72.5 mm, giving a speed factor of 105,125 mm-RPM. The ISO VG viscosity requirement from the bearing manufacturer's chart is approximately 68 to 100 cSt at 40 degrees Celsius — use a grease with a base oil viscosity in this range, not one with VG 220 because "thicker is better." Thicker base oils at high speeds generate churning heat that degrades the grease and cooks the bearing.
Thickener selection determines where and how long the grease can serve. Lithium complex (dropping point above 260 degrees Celsius, good mechanical stability, moderate water resistance) is the workhorse for general industrial bearings up to 150 degrees Celsius continuous. Polyurea (dropping point above 250 degrees Celsius, excellent oxidation resistance, sealed-for-life capability) is preferred for electric motor bearings where regreasing access is limited and service life targets exceed 20,000 hours. Calcium sulfonate complex (dropping point above 300 degrees Celsius, inherent EP properties, outstanding water washout resistance per ASTM D1264 under 2 percent) is the correct choice for wet environments — paper machines, food processing wash-down areas, and outdoor equipment. NCH's Lubri-Lab range covers each of these categories with industrial-grade formulations: their lithium complex EP2 grease (NLGI Grade 2, base oil VG 150) handles the broadest range of general applications, while their calcium sulfonate complex grease provides genuine multi-purpose performance in wet, corrosive, and high-load conditions without needing separate EP or rust-inhibitor additives.
The application method matters as much as the product choice. For rolling element bearings, the correct fill volume is one-third to one-half of the free space inside the bearing housing — not packed full, which is the natural instinct of every mechanic who has ever held a grease gun. Over-greasing causes the excess grease to churn against the cage and seals, generating frictional heat that oxidizes the grease, degrades the base oil, and raises bearing temperature by 10 to 20 degrees Celsius above normal. The regreasing quantity formula is straightforward: G = 0.005 x D x B, where G is grams of grease, D is bearing outer diameter in mm, and B is bearing width in mm. For that 6310 bearing (D = 110 mm, B = 27 mm), the regreasing quantity is approximately 15 grams — about three pumps of a standard manual grease gun. The interval depends on the speed factor, temperature, and contamination exposure, but a reasonable starting point is 2,000 to 4,000 operating hours for a clean, moderate-temperature application. Ultrasonic-assisted greasing using a handheld monitor (UE Systems Ultraprobe 401 or equivalent) takes the guesswork out entirely — you pump grease slowly until the ultrasonic dBuV reading drops to the baseline, then stop. This method reduces both over- and under-lubrication incidents by over 80 percent in every plant I have implemented it.
