Mazda 3 diesel auto due September

Australia's top-selling car, the Mazda 3, is about to be given a boost with the return of a diesel version. It will be available with automatic transmission for the first time, but the price is expected to be north of $35,000, making it one of the dearer models in the new Mazda3 line-up and about $5000 more than it was previously.

After two years at the top of the charts, the Mazda3 has reclaimed the sales lead in 2014 after being overtaken by the Toyota Corolla last year. The arrival of a diesel alternative in September with both manual and automatic transmissions will give the Mazda3 an edge over the Toyota Corolla when it comes to engine options. The Mazda3 is already available with a choice of 2.0-litre or 2.5-litre petrol power and will soon have a 2.2-litre diesel in its repertoire.

The Toyota Corolla, meanwhile, is only available with 1.8-litre petrol power, although a hybrid option using Prius technology is believed to be under consideration.

The diesel alternative with automatic transmission will broaden the Mazda3's appeal; about 12 per cent of Volkswagen Golf sales are of the diesel variant. The previous Mazda3 diesel only accounted for 1 per cent of sales of the model range, but the automatic transmission opens it up to the majority of the market.

“We were hamstrung with the last model by only having a manual transmission,” said Mazda Australia's Steve Maciver.  “About 75 per cent of the small-car market favours automatic transmission so there's definitely potential for a sales boost now that we will have the option of a diesel automatic.”

A super-efficient Mazda3 diesel in Europe sips just 3.3L/100km using the same engine. But the diesel Mazda3 due in Australia, which has an average consumption rating of 5.0L/100km (12 per cent better than before), has been tuned for performance. “With a class-leading 420Nm of torque we see this car as a performance variant,” said Maciver.

The 2.2-litre diesel engine is the same one used in the Mazda CX-5 SUV and Mazda6 mid-size sedan and has 129kW of power and 420Nm of torque. The previous 2.2-litre diesel had 120kW and 360Nm.

Mazda is yet to release pricing of the new diesel Mazda3 but it is expected to priced above $35,000 given it will come as an “Astina” luxury model. A bulletin issued by Mazda this week said it will initially be available in a hatchback bodystyle only.

This reporter is on Twitter @JoshuaDowling