A vehicle system comprises an engine, a motor-generator and a controller. The engine has a combustion mode in which a part of an air-fuel mixture is combusted by spark ignition, and then the remaining air-fuel mixture is combusted by self-ignition. The controller sets a target additional deceleration based on a steering angle, when a steering wheel is turned, and sets an air-fuel ratio of the air-fuel mixture to either one of a first air-fuel ratio and a second air-fuel ratio which is on a lean side, based on an operating state, when the engine performs the combustion mode. The controller controls an ignition timing so as to generate the target additional deceleration in the first air-fuel ratio, and controls a regenerative electric power generation of the motor-generator so as to generate the target additional deceleration in the second air-fuel ratio.