The fuel economy of a Ford Sierra 1983 depends on the engine size and type. Generally, the 1.6L 4-cylinder petrol engine has a fuel economy of around 32 mpg, the 1.8L 4-cylinder petrol engine has a fuel economy of around 33 mpg, the 2.0L 4-cylinder petrol engine has a fuel economy of around 34 mpg, the 2.3L 4-cylinder petrol engine has a fuel economy of around 33 mpg, the 2.8L V6 petrol engine has a fuel economy of around 27 mpg, and the 2.3L 4-cylinder diesel engine has a fuel economy of around 40 mpg.