After the successful introduction of the fourth BMW 7 Series generation in 2001, an inline six-cylinder petrol engine was also supplied from 2003. This engine was the engine known as the M54 already powering the BMW 5 Series, the BMW 3 Series and the BMW X5. The crankcase and the cylinder head are made of a lightweight aluminium alloy in order to cut down weight. Fully variable control for the opening of the inlet and outlet valves helps to make the engine fuel efficient.