CONTROLLER AND CONTROL METHOD FOR VEHICLE

A vehicle including an internal combustion engine and an automatic transmission capable of transmitting and receiving torque to and from an output shaft of the internal combustion engine is controlled. During operation of the internal combustion engine, a process that calculates a diluted water amount based on an operation state of the internal combustion engine is executed. The diluted water amount is the amount of water contained in lubricating oil in the internal combustion engine. Further, a process that controls the automatic transmission such that torque per unit period in the internal combustion engine becomes smaller when the diluted water amount is relatively large compared to when the diluted water amount is relatively small, while continuing the operation of the internal combustion engine, is executed.