Abstract: The present invention is directed to an oil hub cap comprising a cylindrical body for mounting to a wheel axle defining an interior space for holding lubricant oil and a transparent front face. An indicating ring is located within the interior space, such that the outside edge of the indicating ring indicates the minimum amount of lubricant to be contained within the interior space and the inside edge of the indicating ring indicates the maximum amount of lubricant to be contained within the interior space, the surface of the indicating ring between the inside and outside edges being provided with a reflective surface.