Abstract: Rubber compositions for use in tire treads are disclosed. One or more selected styrene-butadiene rubbers of specified glass transition temperatures are blended with a selected type of carbon black of specified physical characteristics. The composition is highly stable in runnability on dry, wet and snowy roads.

Abstract: In an internal combustion engine which incorporates an exhaust gas recirculation system which has an exhaust gas recirculation flow control valve provided at a middle position of the exhaust gas recirculation passage, the control valve being operated depending upon comparison between target and actual values of a control parameter with regard to the amount of exhaust gas recirculation, an auxiliary valve is provided in the exhaust gas recirculation passage in series with the exhaust gas recirculation flow control valve so as to control the cross-sectional area of the exhaust gas recirculation passage in accordance with the opening amount of the throttle valve provided in the intake passage of the engine.