Citroen’s C5 range will now feature a range-topping, 173hp 2.2-litre automatic engine in both saloon and estate models.
The introduction follows the addition of this diesel unit to Citroen’s C6 line-up.
According to the manufacturer, the C5 will offer "an outstanding blend of performance, refinement and economical fuel consumption" when equipped with the 2.2-litre automatic engine.
A fuel economy rate of 39mpg will be achievable on a combined cycle, as well as a 0-62mph time of 9.5 seconds and a top speed of 138mph.
In the C6, the 2.2-litre powerplant has an emissions rate of 175g/km, a figure which Citroen describes as "impressively low", and offers fuel consumption of 43mpg.
A diesel particulate filter system has been fitted in both models to boost their green credentials and a number of innovations, including a parallel sequential dual turbo and a new combustion chamber, have also been developed.
Introducing the new engine options, Citroen said: "The availability of these new models will enhance the reputation of the C5 and C6 as being ultra-comfortable long distance cruisers, aided by the fitment of Citroen’s much admired self-levelling suspension."