A well drilling sub has a body with a threaded upper end for connection into a drill pipe string and a threaded lower end for connection and rotation with an earth boring bit. An axial passage in the body conveys drilling fluid to an outlet in the earth boring bit. Diverting nozzles in the body are in fluid communication with the axial passage. Each nozzle diverts and discharges a portion of the drilling fluid being pumped down the axial passage. Each diverting nozzle has a nozzle axis that points upward and outward and also at a oblique angle. The oblique angle lags a radial plane considering a direction of rotation of the body.