SURELY there must be a catch? How can the new entry-level diesel engine in the Astra offer substantial improvements in performance while actually using less fuel? Thanks to the latest in turbodiesel technology, Vauxhall has made the impossible possible.

The latest addition to the Astra CDTi range, which went on sale last week, uses a more powerful development of the unit already seen in the Corsa and Tigra ranges. The new 90PS powerplant uses a sophisticated variable geometry turbocharger to give a maximum torque output of 200Nm (148lb ft) between 1,750 and 2,500rpm. That represents a 30Nm increase over the Astra's current 1.7-litre CDTi 80PS engine.

On the road this translates to perkier performance, with the 0-60mph acceleration time dropping from 14.0 to 12.7 seconds and the top speed rising from 104 to 107mph. But it is economy and running costs which really matter to diesel drivers - and here the new CDTi really shines. Returning a 58.9mpg average on the combined cycle and an astonishing 70.6mpg on the extra-urban cycle, the new diesel is one of the most economical cars on sale in the UK, and yet it can still offer all the style, space and practicality of the Astra.

The impressive performance is partly due to the introduction of an all-new six-speed manual transmission, which is geared to combine the best in peppy performance round town while maintaining the ability to cruise effortlessly at motorway speeds. So what about the catch? Despite the significant improvements and advanced technology used in the new engine, prices start at £13,895 and it is available in high-value Life, Club and Breeze trim levels. Expect it to catch on quickly!