Cosseting ride: the new Peugeot 308 GT

Diesels deliver low CO2 emissions but they are also prone to produce more noxious fumes and carcinogenic particles than their petrol-powered cousins

Price: £25,945
Engine capacity: 2 litre diesel
Power output (hp @ RPM): 180@3,750
Top speed (mph): 136
Fuel economy (mpg): 70.6
CO2 emissions (g/kg): 1:03

Diesel. Automatic. Stop-start. Not, you would think, the ideal combination for a sports saloon. In the case of the Peugeot 308 GT, you would be right, too – but only just. This car is not an "epic fail", as I think the modern expression goes. Just a bit of a fail.

First, the good – even great – bits. Plenty of praise is due to Peugeot for pioneering diesel-automatic cars – a tricky bit of engineering, though commonplace now, and they were just about the only company to bother to try. Now they have developed clean "Blue HDI" technology, and in the 308 GT we have a torquey two-litre diesel-engined family car capable of the sort of fuel economy and emissions you'd only find on a hybrid a few years ago. I especially enjoyed the "Sport" button that turns the dials blood red, and sharpens up all its responses. Nice.

Yet we also now know that diesels are not actually as nice as they're made out to be. They do deliver low CO2 emissions, as here, but they are also prone to produce more noxious (nitrous oxide) fumes and carcinogenic particles than their petrol-powered cousins. Filters in their exhausts were supposed to be the answer to this, but they can clog up and stop working, and some unscrupulous owners (illegally) remove them. This is why you sometimes see not-so-old diesel cars and vans belching out huge sooty black clouds. Peugeot's new diesel is Euro 6 compliant, and super-clean in principle; but I remain a sceptic about their longer-term performance – ironic when ultra long-life was always supposed to be a diesel virtue.

Less controversial is the cosseting ride that the 308 GT delivers (and in marked contrast to the almost barbarically harsh 208 GTi, by the way). Again, this has always been a Peugeot hallmark, and the 308 sits, rather comfortably, in a fine tradition that dates back to those cushions on wheels the 305, 604 and 504, when Peugeots were a less common sight than they are now. The 308 GT's stop-start function is quick to respond. Not so the auto gearbox, however, and you will find a disappointing lack of urgency when accelerating out of a corner. That is its only flaw. If they didn't call it a GT, and didn't charge quite so much for it, this 308 might be called perfect.

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