AUSTRALIA’S most popular car will also become the nation’s most economical homegrown six-cylinder model when Holden’s model year 2010 Commodore range goes on sale later this month.

Revealed last month as the centrepiece of a raft of changes for the efficiency-focussed MY10 VE Commodore and WM Statesman range, a smaller new 3.0-litre direct-injection petrol V6 for the entry-level Omega and Berlina sedan and Sportwagon will also increase the performance of Holden’s most affordable Commodore models.

Holden is the first Australian manufacturer to produce a direct-injection vehicle, with the same Spark Ignition Direct Injection (SIDI) technology now also gracing the rest of the 3.6-litre VE/WM range.

Holden does not release official acceleration figures for its models, but GM engineers are adamant the Port Melbourne-made V6 makes the first 3.0-litre Commodore since the 1986-1988 VL Commodore quicker than its 3.6-litre forebears.

However, while prices for the rest of the locally-produced large-car line-up remain unchanged, a $700 price increase for the Omega and Berlina (3.0 and LPG) brings the starting price of the updated Commodore sedan range to a new high water mark of $39,990, plus dealer and statutory charges. The MY10 Omega Ute price also increases by $700, to $33,490.

The downsized 3.0-litre V6, developed by General Motors for the Buick LaCrosse and Chevrolet Equinox, is expected to power no less than half of all Sportwagons sold and 42 per cent of all Commodore sedan sales, with the lion’s share going to the volume-selling fleet-favourite Omega.

A similar fuel-injection system was introduced for the Cadillac CTS in 2007 and is already employed by some export versions of Holden’s Global V6, however.

The ground-breaking efficiency measure is hailed as one of the most significant in the 31-year history of the Commodore.

The new engines are mated as standard to GM’s 6L50 six-speed automatic transmission, which delivers a new league of refinement and performance compared with the archaic four-speed auto it replaces in Omega and Berlina.

But it does not extend to the base Omega Ute and LPG Omega sedan, both of which run carryover engines and (four-speed) automatic transmissions.

As such, most but not all MY10 models are differentiated by ‘SIDI’ badging, which Holden decided was less confusing than names such as VE Series II or the widely speculated VF series name, with both the SIDI-equipped Commodore Omega and Berlina body derivatives joining Holden’s ‘EcoLine’ range of environmentally friendlier vehicles.

For now, Holden has focussed on fuel-efficiency with the MY10 Commodore. While E85-compatible and a dedicated-LPG system are at least 12 months away, aluminium panels and other weight-saving measures previously alluded to by former Holden chief Mark Reuss are also likely to arrive as part of a cosmetic upgrade for the VE-series large-car in coming years.

As previously reported, the 3.0L SIDI engine will reduce the official average ADR81/02 fuel consumption and CO2 emissions of the least expensive Commodore sedans by 12 per cent – from 10.6 litres per 100km to a class-leading 9.3L/100km, and from 252 grams per kilometre to 221g/km.

The LF1-codenamed engine, which weighs about 10kg less than the 3.6 it supersedes, also improves the efficiency of the Omega Sportwagon by 13 per cent (from 10.7 to 9.3L/100km) and the Berlina Sportwagon by 10 per cent – from 10.7 to 9.6L/100km – with CO2 emissions falling a respective 14 and 11 per cent.

The new Euro 4 emissions-compliant 3.0-litre Commodore engine produces 190kW at 6700rpm (up from the 180kW of the 3.6-litre engine it replaces) and 290Nm of torque from 2900rpm – down from 330Nm. It runs on standard 91 RON unleaded petrol.

As well as being more efficient than the Toyota Aurion’s 200kW/336Nm 3.5-litre V6 and the Falcon’s current 195kW/391Nm 4.0-litre inline six – both of which return as little as 9.9L/100km with a six-speed automatic transmission – it will compete directly with a new turbocharged four-cylinder engine slated for the Falcon from 2011.

While the 3.0L SIDI six is officially 0.6L/100km more frugal than the base Falcon and Aurion, it is 0.5L/100km thirstier than Toyota Australia’s recently upgraded Camry medium sedan. Its 2.4-litre four-cylinder returns 8.8L/100km – a benchmark that should be shattered by next February’s Camry Hybrid, which promises 7.0L/100km.

Codenamed LL4, the SIDI-aided version of Holden’s 3.6-litre V6 delivers 210kW at a lower 6400rpm and 350Nm of torque at the same 2900rpm – up from 195kW/340Nm and bettering all but the peak torque of the bigger Falcon six.

Fitted to the SV6 sedan, wagon and ute, the Calais and Calais V sedan and wagon, and the long-wheelbase Statesman and Caprice sedans, the larger SIDI engine improves fuel economy in premium Commodore models by between seven and 13 per cent, with the MY10 Calais’ fuel economy improving from 11.2 to 9.9L/100km.

Although the Omega Ute’s (3.6-litre) petrol V6 stays at 175kW/325Nm and the Omega sedan and ute’s LPG engine option continues to offer 175kW/318Nm, engine tweaks will see the Omega sedan LPG’s consumption drop six per cent, from 14.1 to 13.4L/100km.

Average CO2 emissions of 217g/km (down from 230g/km) give the upgraded LPG sedan an official greenhouse rating of six out of 10 – up from 5.5 for the MY10 Omega 3.0 SIDI sedan.

The carryover 6.0-litre Gen IV V8 found in SS, SS-V and so-optioned Calais V and Statesman/Caprice models offers the same 260kW/517Nm with a six-speed automatic (270kW/530Nm as a manual).

The latter’s Tremec TR6060 six-speed manual gearbox, which is shared with LS3 V8-powered vehicles such as the HSV range and Chevrolet’s Corvette and Camaro, features wider gearsets for improved torque capacity and shorter throws, while upgraded synchronisers aim to reduce shift effort and improve precision.

A new 290mm clutch with 24 per cent higher clamp-load is specified, while the master cylinder and clutch pedal ratio are changed to maintain pedal feel. The V8 manual’s gear ratios and final drive ratio are unchanged, at 3.45 for the manual and 2.92 for the auto, versus 3.27 for all V6s.

Similarly, the SV6 manual’s six-speed Aisin AY6 transmission scores a new 257mm clutch with 27 per cent higher clamp-load to match the 3.6L SIDI engine's higher torque output, while fifth and sixth gear synchronisers have been improved to maintain shift feel with the new clutch.

Elsewhere, Holden says significant noise and vibration improvements were achieved for the MY10 Commodore via the fitment of low rolling-resistance Bridgestone Turanza tyres on models fitted with 16 and 17-inch wheels. Each tyre is claimed to be 2kg lighter.

Further reducing friction and drag, the Omega’s standard 16-inch tyres are now specified to run at 270kpa (up 20kpa), while the 17s continue to run at 250kpa and the electronic stability control (ESC) system is recalibrated to suit all models.

Suspension-wise, replacing the rubber bushes in the outer positions of the lower rear control arm knuckles are two new cross-axis ball-joints, which are said to increase high-speed stability, lane-change performance and on-centre steering precision. Handling improvements are also wrought in conjunction with a larger 20mm rear anti-roll bar for models with 18 and 19-inch wheels.

Finally, noise-reduction measures include a new dual exhaust system with larger muffler volume and more advanced back-pressure control, plus a new “front-of-dash and engine bay acoustic package”.

The 3.0-litre V6 Omega and Berlina automatic’s towing capacity is 1600kg, which is the same as manual versions of all other Commodores but 500kg less than the 2100kg stated for all 3.6 SIDI, LPG and V8 models.

Holden said it achieved an average of 7.5L/100km while travelling from Melbourne to Sydney in an MY10 Omega on a single tank of fuel.

To showcase the 3.0L SIDI engine’s fuel efficiency, Holden will enter an MY10 Omega Sportwagon in the 3000km Global Green Challenge (formerly the World Solar Challenge), to run from Darwin to Adelaide over October 24-31.