 Admiral buyers were no longer offered the option of an upgrade to the Chevrolet-powered version; a 5,354 cc V8 was fitted in the Diplomat version of the car.During the 1970s Germany followed general trend of discouraging the addition lead to road fuel, which was followed by a reduction in the octane levels of the "normal" and "super" grade fuels widely available at filling stations.Opel reacted by reducing the compression ratios on all three versions of the Admiral's 2,784 cc six cylinder engine which led to reductions in listed maximum outputs of between and .