The greenest Insignia is a spacious family car with a relatively modest carbon emissions impact

Vauxhall's Insignia EcoFlex is a large family car that has undergone a range of tweaks designed to cut its CO2 output.

In common with other "green label" cars from major manufacturers, the EcoFlex version of the Insignia employs a retuned turbo-diesel engine, revised gear ratios, low-resistance tyres and aerodynamic tweaks to boost fuel economy compared to its standard siblings.

Given the generous size of the Insignia, the EcoFlex model's CO2 score is quite impressive.

At 136g/km the EcoFlex car emits 18g/km or about 12 per cent less than a standard Insignia with the same engine, which scores 154g/km.

Costs and savings

For company car drivers, the EcoFlex model qualifies for 18 per cent benefit-in-kind tax this year, rising to 19 per cent in the coming 2010/11 tax year and 20 per cent in 2011/12. Those figures are uniformly four per cent below the rates for the same car without its green tweaks. A 40 per cent tax payer can therefore recoup the EcoFlex model's £542 premium in about 18 months through tax alone, even before you begin to consider the fuel savings.

By coming in at under 160g/km, the EcoFlex Insignia qualifies for the low-carbon Capital Allowance regime, which allows fleet buyers to write down 20 per cent of the car's purchase cost in the first year, or offset 100 per cent of lease payments against tax.

In addition, reduced fuel use should save an EcoFlex motorist around £110 for every 10,000 miles travelled, or more if fuel prices continue to rise, compared to the standard diesel Insignia. Band E road tax rather than Band G will also conserve cash, with £45 a year saved in the 2010/11 tax year.

Residual values for the standard and EcoFlex editions are projected to be identical, so paying the £542 EcoFlex premium does set the buyer up for slightly higher depreciation.

Taking all the various cost savings into account, and comparing costs with an otherwise identical non-EcoFlex Insignia, a private buyer is likely to break even in a little over three years, a 20 per cent tax payer in about 18 months, and a 40 per cent tax payer in just over a year. Drivers who keep the car longer or who use the car more than the average will of course recoup the cost more quickly and then go on to save more money overall during their use of the car.

Design and equipment

Inside and out, the Insignia looks and feels like a high-quality product. Cabin materials are excellent, seats are firm and comfortable, and the ambience is lifted by attractive flourishes such as bright metal trim pieces and door pocket lighting. Hatchback, saloon and estate models are available.

The EcoFlex package is offered as a option with most trim levels of the Insignia, from the basic to the plush (although not with the sporty SRi variety).

Our 5-door test car came in mid-tier Exclusiv Nav trim, which starts at £20,980 on the road and includes a wide range of convenience features – some of which worked better than others. We found the rain-sensing wipers responded uncannily well, for example, while the dusk-sensing headlamps seemed overly keen to illuminate. The fuss-free electronic handbrake switch made hill-starts effortless, but the twist-and-press multimedia controller next to the handbrake was too easy to hit accidentally. Similarly, the satellite navigation offered good verbal instructions, but delivered them in a very fuzzy and unnatural manner. Rear seat passengers also have to wind their own windows, while taller ones may feel short of headroom.

Driving

Some eco specials look good on paper but are not so great to drive. Thankfully this Vauxhall is not one of them. Despite the gearing adjustments, the Insignia EcoFlex remains easy and pleasant to pilot, with plenty of urge on offer from the 2.0-litre, 158bhp engine. The six ratios available from the manual gearbox – including a very long sixth gear – mean that steady speed running at UK speeds can be done with the engine turning over at a leisurely rate, below 1,500rpm.

A small "shift" indicator that lights up on the dashboard helps to remind drivers when a higher gear would be more economical. There's no downshift reminder, but the engine offers its own unmistakeable hints if the tacho needle drops too low.

The relatively long ratios mean that 30mph urban roads need to be tackled in third rather than fourth gear, to avoid constant cog-swapping, but we soon got used to this quirk. At cruising speed on motorways, the low revs and slippery shape mean the car remains very quiet and refined. Dropping a gear or two allows the driver to tap the considerable power on offer for safe and rapid overtaking.

In our tests we found the car generally comfortable and reassuring to drive. Most lumps and bumps were smoothed out with aplomb, but some surfaces outfoxed the suspension – which has been lowered to reduce the car's aerodynamic drag - transmitting more vibration and oscillation than we'd have liked through to the cabin. Steering and brakes felt lifeless but predictable, while the gearbox in our low-mileage car seemed a little reluctant, requiring a firmer hand than expected.

Crash-test safety scores for the Insignia are very good, while an electronic stability system is fitted as standard to the car, which can help to avoid collisions.

Summary

The Insignia outsold its chief rival, Ford’s Mondeo, in the UK last year, and it's easy to see why. The car offers style, quality and excellent value for money.

The EcoFlex package takes nothing away from the Insignia's winning recipe except CO2. This makes it an excellent choice for high-mileage drivers hoping to cut running costs and lower their emissions.

Vauxhall Insignia 2.0 CDTi EcoFlex
Engine: 2.0 CDTi 16v turbo diesel with particulate filter
Capacity: 1956cc
Max Power: 160PS @ 4000rpm
Max torque: 350Nm @ 1750-2500rpm
Max speed: 137mph
0-60mph: 8.9 seconds
Insurance group: 10E/21E
VED (2010/11): Band E (£110 per year)
Luggage Capacity (seats up/down): 530/1470 litres

Fuel Economy
City: 41.5mpg
Highway: 67.3mpg
Combined: 54.7mpg
CO2 emissions: 136g/km

Model tested: Exclusiv Nav 5-door hatchback
Price on the road, excluding options: £20,980

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