Any car can be greener

Anyone who still drives a car built before 1986, when Australia switched to unleaded petrol, should dump their gross polluter in favour of something newer with a cleaner tailpipe output.

It doesn't have to be brand-new, and even classics can usually be tweaked to make them run cleaner.

That explains why Toyota was prepared to lose money on the original Prius and why the cost of diesel engines - in comparison to petrol powerplants - has been coming down.

Emission regulations have been tightened progressively over more than 30 years until the standard today for the vast majority of vehicles is set at a level called Euro 4, with Euro 5 to follow and Euro 6 - which could be close to zero emissions if some European companies get their way - after that.

Each advance down the Euro emission road has brought an improvement in the green performance of vehicles, with a generally seamless transition - apart from some nasty early unleaded engines - that has no affected owners.

Euro 5 could be very bad news for fans of diesel, as there is a clampdown on nitrogen oxides and exhaust particulates that has Mercedes-Benz predicting the death of this type of powerplant - at least as it's known today.

But Mercedes and General Motors trumpet new technologies that can still make a 25 per cent improvement to the efficiency of the basic petrol engine. Toyota has pioneered an engine that has no power-sapping drive belts - using it in the Prius - and on-demand alternators, electric water pumps and power steering, stop-start engine controls and even active aero adjustments - blanking the grille openings at highway speeds - will be commonplace in coming years, not just on hybrids and fuel- economy cars.

More and more cars are now coming with automatic gearboxes that use more gears for better efficiency - the benchmark is eight speeds - and engine downsizing means a new two-cylinder motor in the Fiat family and an upcoming three-cylinder fuel miser from BMW Group.

J.D. Power forecasts that there will still only be about 160 electric and hybrid cars in showrooms by 2016, but that doesn't mean the rest of the car business won't be much greener inside the next five years.