Mazda’s new CX-7 four-wheel-drive uses a urine-like solution to cut its tailpipe emissions. By RICHARD BLACKBURN and BRUCE NEWTON.
Mazda’s latest four-wheel-drive likes a wee drink.
The Mazda CX-7 uses a special man-made liquid similar to human urine to reduce emissions of oxides of nitrogen (NOx). The compound, called AdBlue, is a mixture of roughly one-third pure urea and two-thirds demineralised water.
It is already widely used in the trucking industry in Europe and Australia and is common in diesel cars in Europe, but Mazda is the first to use the technology on a passenger vehicle in Australia.
The technology, called selective catalyst reduction, involves injecting the urea-based liquid into the car’s exhaust system to turn NOx emissions into harmless nitrogen and water.
The car also has a particulate filter to reduce the amount of soot emitted by the vehicle. Diesel vehicles are a double-edged sword when it comes to environmental impact.
They are more efficient than petrol engines, which means they emit less carbon dioxide, but they also pollute more.
Particulate matter and NOx from diesel vehicles has been linked to a variety of health problems, including respiratory ailments and cancer.
For that reason, diesels don’t rank highly on the Government’s Green Vehicle Guide for environmentally-friendly vehicles.
Regulatory authorities in Europe and the United States are planning to introduce strict new limits on diesel emissions in the future, which will eventually make the urea-based systems mandatory equipment on all cars.
The systems aren't mandatory in Australia, but Mazda is ensuring drivers toe the line with the environmentally-friendly technology.
To guard against forgetful drivers not filling its AdBlue tank, the Mazda CX-7 diesel will cut its maximum speed if the level of AdBlue falls below a certain level.
The car will not start if the AdBlue tank is empty. The 15.5-litre tank is mounted under the rear-floor of the CX-7 and Mazda recommends the task is undertaken by an authorised dealer as part of scheduled servicing.
A gauge and warning lamp warn the driver as the level drops. The AdBlue tank requires refilling every 20,000km and costs about $140 a refill, which works out to roughly $7 per 1000km.
The CX-7 diesel also carries a sticker price premium of almost $5000 over the Sports petrol model (although it also gets a leather interior, satellite navigation and a better stereo), which adds to its comparative running costs.
The new diesel Mazda continues a trend by car makers to reduce CO2 emissions by introducing smaller, less powerful petrol engines and diesel powerplants.
Mazda, which has traded on its sporty image through its “zoom-zoom” advertising tag line, has forgone power for less thirst with the new CX-7.
The car was previously available only as a fuel-sucking, turbocharged petrol model, but the company has introduced a cheaper four-cylinder petrol version that uses almost 20 per cent less fuel.
The diesel variant is even more frugal, using a third less fuel than the turbo. Mazda isn’t the first car maker to turn to less powerful, more fuel-efficient engines in the past months.
Australia’s top-selling car, the Holden Commodore, now comes with a smaller 3.0-litre V6, the smallest engine the car has used in 20 years.
Mazda Australia marketing manager Alastair Doak said customers were beginning to better understand the benefits of driving a diesel car in Australia.
“We have done a lot of market research on why people buy diesel and one of the things that attract people to it is technology, but also people understand that they are using less fuel and that environmental message is strong for those buyers,” he said.
