While the lesser models (Opel Kapitän and Admiral) were also available with a carburetted 2.8 l-inline six, the Diplomat could be had with either a fuel-injected version of this engine (Diplomat E) or with Chevrolet´s 327-V8 (Diplomat V8), now coupled to a 3-speed Turbo-Hydramatic.
В то время, как Kapitän и Admiral имели 6-цилиндровый карбюраторный мотор объёмом 2,8 л, Diplomat оснащался либо аналогичным, но с впрыском топлива, либо Chevrolet 327-V8 (Diplomat V8) с 3-скоростной АКПП Turbo-Hydramatic.