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  The diesel in the Mazda3 is the 2.2-litre common-rail direct-injection turbo four-cylinder used in the larger 6 and even larger CX-7.

Kevin Hepworth road tests and reviews the Mazda3 diesel

It is one of the enduring mysteries of modern diesels. Why can just about every European manufacturer find an automatic to match with a small diesel, yet it is something that remains beyond the comprehension or the ability of the Japanese.

And that is a shame. Mazda's appealing little 3 diesel - and Subaru's Outback diesel, for that matter -- is only going to win the following it deserves when the effective and efficient benefits of the compression-ignition engine are coupled to a self-shifter.

It is a fact of life that Australian drivers, and particularly those in the market for a small city car, have no great desire to reap the considerable windfalls of a diesel by giving up the convenience of an automatic gearbox.   That will cost both Subaru and Mazda sales in their respective segments, something both companies are at least with their public face on willing to live with.

Drivetrain

At least in the case of the Mazda, the company engineers have managed to offer a clutch/gearbox/ratio relationship that makes the drive experience far more relaxed than that in the Subaru where a lack of low-rev torque threatens a stall any time the driver loses focus.

Mazda may have given up a shade of economy although it doesn't show overtly with a handy average of 6.2L/100km during the test week without any effort to drive for efficiency, but they have retained a key benefit of the diesel with good urge coming quickly to hand.  The diesel in the Mazda3 is the 2.2-litre common-rail direct-injection turbo four-cylinder used in the larger 6 and even larger CX-7, albeit a slightly detuned version using a smaller turbocharger than the 6, a variable geometry unit with longer blades for better response.

In its 3 configuration the engine is good for 110kW -- enough for all the top-end speed you could want around town and 360Nm of torque. As a rule it is that impressive torque and its availability (when allowed) from way down in the rev range that makes such a compelling argument for the small turbo diesel.

Driving

In the Mazda the sense of having almost instant pick-up at the tap of the throttle is a comforting and reassuring thing in the morning commute. The gap is there, the car will take it.  The engineering upgrades applied at the launch of the new Mazda3 range last year are, of course, part of the diesel package and without any damper and spring rate tuning adjustments that we are aware of the improvements work just as well for the slightly heavier engine.

Noise from the diesel is well isolated from the cabin and while it is noticeable that there is an oil-burner under the bonnet, at least at idle, the benefits in better noise, vibration and harshness levels seen in the petrol models flow through on the open road.  The diesel ticks all the same boxes that have kept Mazda at the front of the fun-to-drive brigade.

Trimmed to the same level as the Sport Maxx the diesel's interior is thoughtfully laid out, functional and with plenty of soft-touch surfaces. There is little wow factor, but everything that has been done is at a very high standard.

Shoulder room for a couple of larger blokes can get a little tight but not uncomfortable and the seats are well bolstered and generous enough to be comfortable.  Dynamically the car is enjoyable to drive with the new six-speed manual well sorted with the diesel's extra torque answering some of the questions raised over the tallness of the gearing in the petrol car.

The chassis remains tight and the suspension compliant and comfortable while the steering felt like it was a little duller than in the petrol models. While that may be a consequence of the heavier front end, it could also be a slight tuning adjustment to modify the impression of torque steer from the sharp arrival of the engine's urge.

That said, the 3 diesel displayed no tendency to step off the straight and narrow regardless of how enthusiastic the acceleration in a straight line. Jumping the accelerator too suddenly and too early in a corner will elicit a sense that the front wheels want to escape, yet it is not uncomfortable and certainly not uncontrollable.

BOTTOM LINE: Appeals on a lot of levels, just not an automatic choice.

Mazda3 diesel

Price: $29,715
Engine: 2.2L/4-cylinder turbodiesel 110kW/360Nm
Transmission: 6-speed manual
Economy: 5.7L/100km claimed; 6.2L/100km on test

Rivals

Hyundai i30 CRDi: $22,890
Peugeot 308 HDi: $30,690
VW Golf 77TDi: $28,690