A vehicle system includes: an internal combustion engine including an electronically-controlled throttle valve configured to change throttle opening degrees in a step-wise manner among at least three selectable opening degrees, and being mounted on a vehicle; and a control device configured to control the vehicle. The control device includes a required throttle opening degree setting component and a first throttle opening degree selecting component. The first throttle opening degree selecting component is configured to: select, at the time of acceleration of the vehicle, a first throttle opening degree that is greater than the required throttle opening degree and is the closest to the required throttle opening degree; and select, at the time of deceleration of the vehicle, a second throttle opening degree that is smaller than the required throttle opening degree and is the closest to the required throttle opening degree.