A level detector comprises an array of light emitting devices mounted in a line parallel to an array of light receiving devices, the arrays being mounted within a housing capable of internally reflecting light from the emitting devices to respective receiving devices unless the respective parts of the level sensor are immersed in liquid. Lubricating compositions containing reaction products and adducts exhibit improved Timken Load properties. The display provides a consumer with \u201cat a glance\u201d visual information on current usage.