##Superb test--right## IT has six cylinders, is beautifully balanced and produces the seamless flow of power that makes driving a delight in all conditions. But even the finely-honed Volkswagen Group 2.5-litre power unit conforms to the turbodiesel 'norm' by improving with age.

Given that it behaved with such decorum when it arrived at Fleet Towers last summer, the gem of an engine under the bonnet of our long-term Skoda Superb test car seemed like it might prove to be the exception to the rule.

Yet as if by magic, the 155bhp motor has swept this impressive car along with even more aplomb since its digital distance recorder overtook the 8,000-mile mark.

Probably the most refined compression ignition engine available at its price in the fleet sector, it is mated with a six-speed manual gearbox in our Comfort version. And, since the motor punches out its ample maximum torque of 228lb-ft when it is spinning at only 1,400rpm, our car has spent a lot of time loping along in the highest cog.

At the opposite end of the gearing range, first is fine for heavy-load starts, such as when towing, but is generally too low in normal conditions, where the sudden surge of power from the turbo can send the car lurching ahead and calls for rapid selection of second gear.

But back to sixth, which can be used more than you would expect, thanks to the prodigious amount of power on tap. Making only a discreet growl on the odd occasion when it is worked hard, the Superb is quiet at all times, but particularly so in cruise mode, when the tall ratio has it wafting along motorways in such a relaxed manner that the difference between 10 and 200 miles is hardly noticeable.

I thought the car's computer was being a tad optimistic when it first gave returns of more than 50mpg on long trips, but working out the averages on a tank-to-tank basis has showed it to be correct.

Urban and heavy-footed driving sees economy dip to the mid-40s mpg, but my overall figure shows just how wallet-friendly heavy-oil technology has become, particularly so in a car that has limousine-like proportions in the rear and a huge boot for good measure.

By any yardstick, the big Skoda's build quality, fit and finish and spread of equipment add up to high value business transport, but after 10,000 miles, our six-cylinder version has proved to be Skoda's biggest surprise to date. It might be built in the Czech Republic and have a badge that some regard as trailing in the image stakes, but this Superb is a delightfully understated performer that lives up to its unlikely model name.

The Skoda fully deserves to be judged against some of the better-respected premium brands. Company car tax bill (22% taxpayer): £89.76 per month