JUST as most auto manufacturers are turning their backs on diesel to plug into electricity one maker - known for its fine engineering and innovation - has launched an all new diesel engine.

But Mazda's big 3.3 straight-six cylinder is cleaner and more efficient than any yet made, claims the Japanese firm.

It features in the new CX-60 3.3 e-Skyactiv D, a recently introduced large family SUV designed to rival models such as the Land Rover Discovery, BMW X3 and Audi Q5.

With ultra-low CO2 levels and vastly diminished NoX stats, it alters drivers' perception of a fuel that nevertheless offers considerable advantages over petrol but has recently fallen out of favour through pollution fears.

In fact, the diesel variant of the smart CX-60 - which was launched in plug-in petrol form last year - holds several significant gains over its electrified brother.

For a start, it's considerably more frugal, maybe stretching a gallon by 10 miles or so, and with oodles more torque it's a better drive and an improved tow car.

The mildly hybridised six-cylinder engine is positioned lengthways and turbocharged and available in two states of tune delivering either 197bhp or 251bhp. Only the higher powered models are available with four wheel drive.

One of the features of a straight six engine is that it generally is better balanced and smoother than a V6 counterpart.

Certainly, that in the Mazda impresses for its refinement and general quietness, although you can detect a slight diesel 'clatter' at idling speed. This soon disappears to be replaced by a distant but pleasing hum as speeds mount.

The power unit is complemented by an excellent eight speed automatic that can be controlled by steering wheel paddles. Changes are silk-smooth and well judged. It revs freely and feels quicker than its statistics suggest - 0 to 62mph in under eight seconds for the 251bhp model.

Driving on pleasantly deserted Scottish A-roads, the more powerful version feels well planted and composed despite the switchback nature of the route. Corners are taken flatly without drama as the tyres bites into the road surface. Steering is correctly weighted with a degree of feedback and the tall stance allows vision through many of the bends.

Even the inevitable potholes fail to destroy the CX's composure. The story is similar behind the wheel of the 197bhp version, though it lacks the mid-range thrust of its big brother.

The CX-60's styling gets the thumbs up from most onlookers. The trademark Mazda nose with huge grille is immediately recognisable and its designers have managed to make the tall five door more attractive than most other high-riders.

The story is similar in the cabin. Lots of soft touch plastic mouldings, fine leather and clear dials make the driving environment both appealing and relaxing. Maybe not quite up to Audi or BMW levels of luxury, but very close.

Although we will have to wait for the CX-80 before a seven-seat option is offered, space within the CX-60 is ample for five adults. Luggage room too is generous with 570 litres of cargo room before the rear seats are folded. The load platform, however, is quite high.

Equipment levels are generous, as is Mazda's style. Electric front seat adjustment, sat nav, electric tailgate lift, Apple CarPlay and Android Auto are standard across the range.

Prices start at £42,990 with the more powerful version costing from £45,630. Very appealing tags compared with rivals.

It's always interesting to see a car designer refusing to follow the herd, and certainly Mazda's biggest engined model has a lot going for it.