THE diesel Sonata is a nice example of a modern diesel passenger car. A very short drive at the national launch last week revealed the engine is a good, smooth diesel.

The meaty driveability is a positive, with a healthy supply of torque available quite early in the rev range. The turbo gets things going from around 2000rpm and you can leave it in a lower gear and allow the engine to lug the car along with little effort.

Ride the torque band, which is about 2000rpm wide, and you can move along quite swiftly. It is by no means a performance diesel, but is no slouch either.

What was surprising was just how quiet the 2.0-litre diesel is. Hyundai has done a great job in isolating the noise and vibration harshness of the powerplant.

You could expect such an affordable diesel model to clatter and carry on, especially at idle, but the Sonata diesel is quite refined. It is, of course, louder than its petrol sibling, but it is one of the quieter diesels around.

We were only able to drive the five-speed manual version, which proved to be adequate given the price of the vehicle.

But it does feel like it could do with an extra cog for highway cruising. It sits at 2000rpm at 100km/h, which is fine, but it would be interesting to see if an extra gear would allow for a lower rev rate and cruising speeds.

The gearbox itself feels a bit clunky too. It clutch is light enough, but there is a lack of generally precision that is associated with its European and Japanese rivals.

If you like the driveability of the diesel, the Sonata CRDi is worth a look. A miserly diesel also has environmental benefits of low CO2 levels.

But if you are considering a diesel for purely financial reasons, you might want to break out the calculator. On the day of writing, regular unleaded in Melbourne cost $1.59 a litre as compared to diesel at $179.9 a litre.

Comparing automatic models and going by the official consumption figures of seven litres per 100km for the diesel Sonata and 8.4L/100km for the petrol, if you did 20,000km a year the diesel Sonata would use 1400 litres of fuel, while the petrol model would use 1688 litres per annum.

That’s great, but the difference in fuel prices all but wipes out the advantage. At today’s price, the diesel Sonata would cost just $79.23 less to run a year than the petrol model.

Take into account that the diesel Sonata costs $2500 more and it makes less sense. In fact, at this rate it would 31 and a half years to repay the purchase difference and, if we believe the skeptics, there might not be any petrol or diesel left by that stage.

Of course, this calculation relies on the price difference between petrol and diesel staying put, but it's not clear what will happen to the value of either fuel.

There is also the question of resale. It is expected the resale value of a diesel Sonata would be higher than the petrol model, but that’s not completely clear given the limited amount of diesel passenger cars in Australia.

Also, if diesel fuel becomes more expensive and therefore less beneficial, it’s unlikely the resale of diesel passenger cars will sit far above petrol equivalents. Of course, these calculations apply to all diesel engines that come with a premium over petrol, not simply the Sonata.

While it was only a short drive, our run in the diesel Sonata revealed its chassis is generally well configured for Australian conditions. The suspension has been tuned well considering the target market. It is quite compliant and does a good job at absorbing the bumps on the test route, which was held on some fairly challenging roads.

Hyundai has altered the steering and while it does feel faster, it also feels a little nervous. We’d need to test the old and new car back-to-back to see if it is an improvement.

The bumpy roads also reveled the Sonata has some steering rack rattle issues when you push through some corners with uneven surfaces.

Inside, the Sonata is adequate, although the interior design and surface quality is a step below its European and Japanese rivals.

A strong point of the Sonata, be it petrol or diesel, is the standard five-year/unlimited kilometers warranty that includes one year of roadside assistance.

All up the diesel Sonata is an impressive and economical car that is surprisingly quiet.

It’s well worth a look if you like the feel and torque delivery of a modern diesel, but just make sure you do the sums if you are selecting a diesel for financial reasons alone.