KIA Australia has introduced a new turbo-diesel engine into a revised Sorento SUV range, while at the same time reducing the size of its petrol V6 engine to 3.3 litres.

Reducing the V6 engine capacity (from 3.8 litres) has also resulted in a reduction of the entry price to the Sorento range, down by $3000 to $33,990 for the automatic transmission-only LX model.

Diesel-engined models are priced at a $3000 premium over the petrol versions, though the availability of a manual gearbox in the Sorento CRDi (the only variant in the range equipped with a manual) means that the entry-level diesel is priced from $34,990.

First launched in 2002, the Sorento quickly became the top-selling Kia model in Australia but has lost some ground – along with most Kia models – as new and updated entrants arrived in the now highly competitive medium SUV market.

Kia Australia sales and marketing chief Bill Gillespie said there are now 21 vehicles competing in the segment and diesel-engined models have accounted for the sharp growth.

He expects Sorento sales will double to around 200 a month, with the new diesel models accounting for 80 per cent of sales.

The new 2.5-litre CRDi (common-rail direct-injection) turbo-diesel engine, which will also appear in the Sportage from next week, was developed by Kia at its German development centre. It uses a Bosch direct-injection system and a Garrett variable-geometry turbocharger to reduce turbo lag.

Kia's Euro IV-compliant turbo-diesel develops 125kW of power at 3800rpm and 393Nm of torque at 2000rpm, with at least 290Nm available from only 1300rpm through to 4000rpm.

Fitted to the Sorento, it returns a combined 8.5 litres per 100km in the five-speed manual base model. With an 80-litre fuel tank, that gives the CRDi LX manual a range of some 940km.

By comparison, the new alloy-block 3.3-litre petrol V6 with continuously variable valve timing produces 180kW at 6000rpm and 309Nm at 4500rpm, and returns 10.9L/100km with the five-speed tiptronic-style auto for a range of 733km.

This is 16kW and 44Nm less than the previous 3.8-litre petrol V6 engine, which naturally results in poorer performance (0.7 seconds slower from 0-100km/h at 9.2 seconds). On the plus side, fuel consumption is much better – down by 1.1L/100km.

Importantly, the Sorento's class-leading 2800kg braked towing capacity is unchanged. This enables both the petrol and diesel models to tow bigger boats and horse floats, though we would suggest that the turbo-diesel should be chosen for such chores.

Mr Gillespie said that Sorento's superior towing capacity, along with genuine off-road ability due to its ladder-frame chassis and dual-range 4WD system, provides the vehicle with a distinct market advantage.

He also points to pricing as a key ingredient to doubling sales, claiming it is thousands of dollars cheaper than comparative models.

Against its Korean rivals, Kia claims the Sorento diesel is the same price as the smaller-engined 2.0-litre Holden Captiva, $2000 less than the 2.2-litre Hyundai Santa Fe and $4000 less than the Hyundai Terracan (with a less powerful 2.9-litre engine).

With the petrol model, Kia says the 3.3-litre Sorento undercuts the less powerful Captiva and Santa Fe by $2000 and $4000 respectively.

Active front head restraints have improved Sorento’s crash rating (four stars in Euro NCAP) and all models in the range now have alloy wheels and a roof-mounted trip computer in a revised interior.

ABS brakes, driver and front passenger airbags and front seatbelt pre-tensioners are also standard across the range. Top of the range EX-L models also get side curtain airbags.

Base LX models are fitted with an Eaton limited-slip differential, but EX and EX-L models are equipped with switchable standard electronic stability control.

However, because the ESC is only a basic throttle-control system and therefore does not employ the ABS, it does not operate when four-wheel drive is selected.

As well as ESC and the automatic transmission, the EX model gains larger 17-inch alloys, leather steering wheel and cruise control.

The EX-L, priced from $41,490, offers charcoal leather with red stitching, an electric sunroof, rear spoiler, dual-zone climate-control air-conditioning and black woodgrain centre console and door trim.