The specification of the new Mini Cooper D (for Diesel) includes a set of figures that could bring a glow of pride to your social conscience: urban fuel consumption, 50.4mpg, extra-urban, 76.3mpg, com-emissions, 118 g/km.ined 64.2mpg, and CO2 If you think that might add up to dreary performance, don’t worry, a 0-62mph time of 9.9sec is reasonably brisk and top speed is 121mph.

But there is a figure that might not cheer you quite as much. The Mini Cooper D’s price (there is no basic diesel) starts at £14,190 and while the car has a high level of equipment including comprehensive safety systems, air-con-ditioning is £660 extra. The second-generation Mini was launched only in Cooper and high-performance Cooper S forms last November. Now they are joined by the 108bhp 1.6litre diesel — using PSA Peugeot Citroën’s outstandingly efficient HDi engine — and by the 94bhp 1.4litre petrol Mini One at £11,595.

Noise and vibration can be a problem for diesel-powered small cars; not in the Cooper D, though, and with 240Nm of torque (260Nm with overboost for brief periods and the same as that for the Cooper S) from 1,750rpm and with a six-speed gearbox as standard, the car lopes along.

I checked fuel consumption on the (optional: £100) trip computer and saw 53mpg after driving hard over a 30-mile test route comprising Oxford traffic, motorway and rural roads, with no attempt to drive economically.

The Mini One, also with six-speed gearbox, managed a fraction under 40mpg when hustled over the same route. Its official combined figure is 49mpg and CO2 emissions are 138g/km (16 per cent better than the outgoing Mini One). Both cars had covered only a few hundred miles and their engines were still tight.

The One’s engine, smooth, willing and allied to a very pleasant, light-to-use, rapid-shifting gearbox, was thoroughly enjoyable. Unlike the diesel, maximum torque of 140Nm at 4,000rpm is modest and the engine needs to be revved hard to get reasonable performance. Handling is a big plus; very sportscarish.

Zero to 62mph takes 10.9sec and top speed is 115mph. Motorway cruising was remarkably quiet with just a little wind noise. I was very impressed.

The latest Mini might look like the previous generation but every external feature and body panel has been changed, the engines are better, the suspension has been improved for really enjoyable and responsive handling with superior ride, the redesigned interior has more space, and head airbags are fitted.

Buyers considering the diesel need to do some arithmetic about its cost and economy compared with their typical annual mileage. The Mini One proved delightful on brief acquaintance but like the D, add £660 for air-conditioning. And there is a tempting panoramic glass sunroof on offer for all Minis at £670 — great in glorious spring weather and able to cheer up a grey day.