The season concluded with the Mexican Grand Prix at the Autódromo Hermanos Rodríguez in Mexico City, and Gethin was back on form, qualifying a season best 10th, over half a second ahead of Hulme. He raced strongly again, keeping the faster car of 1964 world champion John Surtees, in the car bearing his name, behind for a number of laps. However, the McLaren's reliability issues reared their ugly head again, and he slowed and finally stopped with engine failure on lap 28.