Vauxhall Astra

All that looks set to change, however, as in the future any diesel that meets the strict Euro 4 emissions levels automatically bypasses the black pump penalty. Vauxhall is the first to meet the green target with its 1.7-litre CDTi Astra - but does the newcomer still pack a torquey enough punch?

The 16v turbodiesel uses second- generation common-rail direct-injection technology to put out 79bhp. That may not sound much, but a very accessible 170Nm of torque is produced between 1,800 and 2,800rpm, and the Astra rarely feels underpowered.

The 0-60mph sprint takes 13.5 seconds, while the top speed is 107mph, and although this performance may be impressive, it soon pales into insignificance when you start to look at the new unit's miserly running costs.

With CO2 emissions of 124g/km - only 6g/km more than that of a Smart City Coupί¿½ - and the Euro 4 tax relief, the Astra falls into the lowest company car tax band of 15 per cent. And the fuel bills are likely to be equally penny-pinching - combined economy is a staggering 61.4mpg, making the Astra one of the most efficient cars around.

Turn the key and there is a familiar diesel rattle, but the powerplant soon settles. On the move, the engine noise is far from intrusive, but you are well aware that it's not a petrol unit.

In Club specification, the five-door CDTi Astra is ΂£13,275 - ΂£400 more than the outgoing 1.7-litre DTi model, but still ΂£575 less than Ford's 1.8-litre Focus TDCi LX. An Eco version is also available with aerodynamic add-ons to increase fuel economy to 64.2mpg.

This new oil-burner sends Vauxhall to the head of the value diesel car chart, and at the same time throws the gauntlet down to rival manufacturers.