It took me longer than I expected to appreciate the Cerato diesel. Kia's ability to design good cars has skyrocketed over the past few years, and I was quite looking forward to trying this one, but for the first couple of days it seemed disappointing. I suspect that some customers may be put off while test driving a demonstrator, and that would be a pity because there's a lot of good stuff going on here.It seems fair to assume that most people who embark on a test drive - whether with a view to buying or writing about the car in question - will set off in an urban environment of some sort. This is not where the Cerato scores. There's a vagueness to all the major controls (particularly the gearchange) which makes town driving a chore and suggests that the car will be clumsy and uncomfortable in all circumstances.In fact this isn't true at all. On country roads the Cerato turns out to be a bit of a goer. Kia has developed a policy of giving its cars soft springs and nicely tuned dampers. As a result, there's a lot of body movement but a minimum of wallow, which produces a fine compromise between ride and handling. Once you're in tune with the Cerato's strengths, you'll find that it's far more nimble than early impressions would suggest.The turbo diesel engine likewise leaves you to find out its best points rather than advertising them right from the start. It's quite a small unit, at just under 1.5 litres, and it doesn't like to rev, but it produces a very useful 100bhp. Although that does not translate into especially exciting performance figures, it does mean that the CRDi spanks along quite smartly. Bearing in mind its most obvious role in life (which probably doesn't involve taking part in many track days), I'd say that it has every bit as much power as it needs.The engine is also reasonably quiet, splendidly economical and very sparing in its production of CO2 - the 129g/km rating puts the CRDi in the 18% Benefit In Kind band. All of this justifies the use of the 1.5-litre engine; if there was ever a temptation to abandon it in favour of the two-litre turbo diesel found elsewhere in the Kia range, it was wisely avoided.There's nothing particularly fancy about the interior, which is straightforward Kia, but it's comfortable enough with seats which are supportive enough for the job. More precisely, I managed several decently long trips without once having the slightest twinge of back pain, which is not often the case. There's also enough room front and rear to make the Cerato reasonable transport for four adults with a combined height of 24 feet.Luggage room seems less impressive by comparison, partly because the boot floor is quite high. Kia claims a volume of 538 litres with the rear seats in place, though I suspect this figure assumes that you're loading up to roof level. With the seats down, the relevant statistic is 1494 litres.LX is the higher of two specifications for the Cerato, though there's not much in it. The GS, which is £750 cheaper, loses out only in that it has steel wheels rather than alloys, and does not have the front foglights or body-coloured side mouldings of the LX.Standard equipment on both models includes ABS, EBD, Brake Assist, six airbags, an audio system with CD and MP3 players and electrically adjustable and heated door mirrors. The test car was a hatchback, which is the only option for the GS, though you can also buy an LX saloon for the same £10,995.On the basis of this test, any of the three cars in the diesel range seems a good bet, but it took me a long time to come to that conclusion. The Cerato CRDi is certainly a car of which first impressions are not necessarily to be trusted. Engine 1493cc, 4 cylinders Power 100bhp Transmission 5-speed manual Fuel/CO2 57.6mpg / 129 g/km Acceleration 0-62mph: 12.5 seconds Top speed 107mph Price £10,995 Details correct at publication date