Hyundai CDX

Refined and punchy, yet economical, the Sonata's new 2.0-litre oil-burner makes far more sense for UK buyers than the thirsty, weak 2.4-litre petrol unit. The Hyundai saloon is frugal, roomy and well equipped - it's just a shame the ride, material quality and styling aren't up to the same standard as the best European models.

It's been a good six months for Hyundai. First, in October, the Korean giant launched the revised Getz, then an all-new Santa Fe arrived. And there have been additions to the Coupé and Tucson line-ups, too. As a result of all this activity, the range is looking stronger than ever.

Yet even though a new version went on sale last year, its Sonata remains a weak link. With bland styling, soft suspension and a thirsty 2.4-litre petrol engine, it's not one of our favourites.

Now, Hyundai has addressed the latter problem by introducing an excellent new 2.0-litre turbodiesel. The 141bhp unit has common-rail fuel injection as well as a particulate filter, and is available mated to a six-speed manual gearbox or a four-speed automatic.

To see what buyers can expect, Auto Express drove the flagship CDX in self-shifting guise. Covering 0-62mph in 11.3 seconds on the way to a top speed of 124mph, it is a respectable performer. And with 316Nm of peak torque between 1,800 and 2,500rpm, mid-range acceleration is strong - certainly much better than that of the petrol version.

What's more, the diesel is refined and free of vibration. And even though the auto isn't the most responsive, it changes gears smoothly. Combined economy is good at 37.9mpg, and the manual car is expected to achieve at least 48mpg.

Yet while the engine is a definite improvement, Hyundai hasn't made the same leap in other areas. Although the ride is soft, the car thumps heavily over potholes. And the inert steering is still some way behind that of European rivals. Inside, however, the CDX is well specified, with standard leather seats, and air-con, plus cruise and stability control. But the plastic steering wheel is slippery to the touch, and material quality elsewhere is only average.

At least there's lots of headroom and legroom, while the 462-litre boot is big. So although the Sonata is far from perfect, the introduction of this new diesel engine is another example of Hyundai's rapid development.