Bearing Grease Life vs Temperature Calculator

Exponentially: each 15 K above the 70 °C reference halves expected life, and each 15 K below roughly doubles it (the grease-industry halving rule — standard lithium grease life halves roughly every 15 K above 70 °C (SKF/Schaeffler relubrication guidance)). A sustained 30 K overshoot quarters the life — which is why a 'small' cooling problem is never small over the years.

Around sustained 90–100 °C the economics flip: standard lithium thickener oxidises so fast there that even halved intervals chase a dying lubricant. Polyurea or lithium-complex greases with synthetic base oils hold service temperatures of 140–160 °C and restore sensible intervals. Mind compatibility on the changeover — lithium and polyurea thickeners are classically incompatible; purge thoroughly or strip and repack rather than mixing.

It is the engineering linearisation of the Arrhenius equation over the normal operating window, adopted by the relevant standards because it matches test data well within ±20–30 °C of the reference. Far outside that window (or where a different failure mechanism takes over, e.g. mechanical wear) the rule loses authority — treat extreme extrapolations as indicative only.

The hot-spot (the hottest point of the insulation/material), because chemistry happens at the hottest spot. If you can only measure surface or ambient, add the typical rise for your equipment class — datasheets usually state hot-spot rise over ambient at rated load — and remember intermittent peaks age the asset during the peak hours, not the average.