An ECU is applied to a hybrid vehicle that is equipped with an internal combustion engine and a second motor-generator, which are configured to output a driving force for running. The hybrid vehicle is configured to run with the internal combustion engine in intermittent operation. Also, the ECU is configured to calculate an amount of dilution water that is mixed into oil in the internal combustion engine to dilute the oil. The ECU is configured to operate the internal combustion engine when the amount of the dilution water becomes larger than a first threshold.