Mazda CX-7Click for more photos

Mazda CX-7

  • Mazda CX-7
  • Mazda CX-7
  • Mazda CX-7

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.