Abstract: A method for controlling an internal combustion engine includes providing an internal combustion engine having an exhaust camshaft phaser and a knock sensor. A second step includes starting the internal combustion engine and receiving a first knock sensor signal from the knock sensor. A third step includes determining a first octane rating based on the first knock sensor signal and an algorithm. A fourth step includes communicating a camshaft timing change to the exhaust camshaft phaser if the first octane rating is less than 100%.