NOT the fastest Jaguar I have driven nor the most silent, but the latest XF 2.2 diesel is, without doubt, a big cat for today.

The reason being the fact that the powerful 190ps power unit returns an astonishing 53.3mpg on the combined cycle for a carbon emission figure of 149g/km.

An impressive figure for a £42,000 top executive car and proof indeed that the company aims for pole position in the race to produce the most economical large diesel while retaining the traditional Jaguar performance credentials.

The engine is a 16-valve four-cylinder common rail diesel of 2,179cc in a north-south configuration , featuring a water-cooled turbocharger, low-friction pistons, new injectors and new crankshaft.

The configuration of the engine allowed Jaguar engineers to add a new oil pan and new electronic systems affecting the crankshaft to allow the car's intelligent stop/start system to operate more efficiently.

The Jaguar stop/start aims to reduce the prolonged time spent in the shut-down and start-up phase usually experienced in some systems - which can be annoying.

The Jaguar system overcomes this partly through the inclusion of a new crankshaft sensor and fuel rail pressure holding system meaning the engine needs less time to restart.

This is best demonstrated when approaching a busy roundabout, in situations where the driver briefly brings the vehicle to a stop, only to move off again quickly.

In conventional systems the engine needs to shut-down completely before restarting again, leading to often frustrating delays in getting going.

The Jaguar system is able to restart the engine while its shifting down from as little as 400rpm meaning it does not need to come to a stop and drive is restored more efficiently.

This system proved itself time and time again during my test drive and won me over to the benefits of stop/start, something I have never previously liked.

The system is calculated to increase overall fuel efficiency between five and seven per cent which is a lot.

Another new feature is an advanced eight-speed ZF automatic gearbox with seventh and eigth ratios effectively acting as overdrive gears.

This allows the 2.2 engine to deliver swift responses and settle down to effortless motorway cruising in the celebrated Jaguar style.

Although particular emphasis has been given to sound deadening there is a definite diesel growl audible inside the car but it is a pleasant beat and in a way adds to the excitement of the car.

This car goes a very long way to prove that not only can a four-cylinder engine deliver the performance goods in a car if this size it can also illustrate that the Big Cat can be a very frugal creature when need arises.