It's time for the most important New Car of the year. This is the New Jaguar XF, the new car will feature the all new 2.2-litre four-cylinder diesel which can return up to 50mpg.

The new super-frugal engine is one of a number of updates for the 2012 model year exec. The New Jaguar XF will debut at the New York Motor Show in a few weeks’ time and goes on sale late next month, with the first cars hitting the road in September. Among the changes are a comprehensive facelift, improvements to cabin quality and updated dampers to improve the ride and handling.

The big change is what’s under the bonnet. It’s not only the 188bhp turbo diesel that’s new; it has an eight-speed auto box, and a stop-start system.

The new XFs powertrain is a crucial addition to the XF range, as it allows Jaguar to compete with small diesels such as Audi’s new A6 2.0 TDI, BMW’s 520d and the Mercedes E220 CDI.

Jaguar say the new engine with have combined economy of 52.3mpg, CO2 emissions of 149g/km. The figures are better than those for the 3.0-litre V6 diesel XF, which returns 42mpg and 179g/km respectively – although it trails the 520d, which posts 54.3mpg and 137g/km.

This means the 2.2-litre will be the cheapest XF to run. Jaguar hope the car will do 800 miles between fill ups; the new engine sits in road tax band F, giving a road tax bill of £130 a year. The company car tax rate is 21 per cent.

Keep an eye on the uknewcars website for the best dealers around on the New Jaguar XF