The 1.9 TTiD Saab engine is now available in all 9-3 Vector Sport variants.
The engine was previously only associated with the top of the range Saab Aero model.
The Aero has achieved fuel consumption of 50.4mpg for the saloon, and an exceptionally low CO2 emissions rate of just 149g/km – comparing well with the 2.8V6 petrol engine.
David Pugh, of Saab Great Britain, said: "The addition of the TTiD engine to our Vector Sport model means that we can offer top level diesel performance with superb fuel efficiency in a greater number of our cars – this really is putting technology in a price range that has never been seen before."
The 1.9 TTiD also produces 180 horsepower (132kW) and 400 Nm of maximum torque, which compares favourably with the two-litre diesel Mercedes Benz E class engines.