IF you are standing in traffic alongside a noisy Jaguar X-Type, don't be alarmed because there is nothing wrong.
Chances are that it is one of the diesel-engined versions that is virtually only idenifiable when idling.
On the open road the oil-burners are visual and audible clones of their petrol-powered counterparts. It is only when stationary that the tell-tale clatter of the diesel engine becomes apparent, and even then it is relatively refined.
Jaguar was desperate to get this car to market, together with the estate version, to give the X-Type the sales boost it so badly needed.
Although an undoubted success, the X-Type failed to match Jaguar's ambitious hopes for it quite as quickly as planned. The problem is not with the car, and it is certainly not with the booming British market, but elsewhere in Europe.
In countries such as Italy, the new car market crashed, to the extent that some of the major players may even now suffer terminal injuries.
Jaguar's future looks assured, however, but only if it can broaden the X-Type's appeal, especially by conquering the diesel market. On mainland Europe diesels account for the lion's share of sales, and in Britain they are soaring.
Being part of the giant Ford empire gives Jaguar access to a wide range of turbodiesel engines, some of which are already to be found beneath the bonnets of its Volvo, Ford and Land Rover stablemates.
First to arrive was the two litre version, with an engine borrowed from Ford's impressive Mondeo TDCi. This broadens the appeal of the tax-friendly X-Type in the junior executive sector of the market.
The engine is a nice one, with an output of 128bhp, and endows the car with the sort of performance with which even the most lowly of Jaguars is synonymous.
With 243 lb ft of torque, or pulling power, there is acceleration to 60mph in nine and a half seconds, and a top speed of 125mph.
The figure for carbon dioxide exhaust emissions is well under 155 grammes per kilometre, which puts the car into the lowest benefit-in-kind tax bracket.
Throw in a choice of manual and automatic transmissions, plus two or four wheel drive, and the X-Type range covers most eventualities. The diesel option is also available on the new estate model, and will be followed by a larger 2.7-litre V6 oil-burner soon.
Even without the diesel and estate options, the X-Type managed to find more than 15,000 buyers a year. Nonetheless, diesel sales are up by almost half, and currently account for a quarter of all new registrations.
The Jaguar is typical of the new generation of sophisticated diesel performers, which are virtually indistinguishable from their petrol equivalents.
Once on the move there is really no difference in smoothness or quietness, with the only tell-tale sign being the enormous mid-range pulling power of the diesels, thanks to their superior torque. The other big difference is economy, with 40mpg being quite realistic, together with enhanced second-hand values.
The only fly in the ointment is the opposition, with strong alternatives from BMW, Volvo and Mercedes.
For example, a Volvo S60 D5 S at £20,880 takes some beating, as does the hugely impressive BMW 320d ES at £20,995.
FAST FACTS
Jaguar X-Type 2.0D Classic
Price: £19,995
Mechanical: 128bhp, 1998cc 4cyl turbodiesel engine driving front wheels via 5spd manual gearbox
Max Speed: 125mph
0-62mph: 9.5secs
Combined mpg: 50mpg
Insurance Group: 14
CO2 emissions: 149g/km
BiK rating: 15%
Warranty: 3yrs/ unlimited miles; 6yrs antirust; 3yrs paint