Though the big hype about powering cars of the future is in the form of switching to hybrid formats and to fuel cells, most of the economy and emissions improvements in the medium term is more likely to involve changes to conventional engines and transmissions.

We're already seeing these in some production cars, with the use of electronics to manage engine systems more accurately, and in increasing use of clutchless automated manual gearboxes.

More automatic transmissions using the constant velocity (CVT) system also save significant amounts of fuel, and we are also to have more cars in the immediate future using 'stop-go' engines which turn off completely when the car is stopped in traffic and restart instantly when the accelerator is pressed.

In Europe, with the diesel revolution which will this year have almost half of all cars sold here with diesel power, the overall fuel economy has improved enormously in recent years while harmful emissions have equally dropped substantially.

Improvements in diesel technology such as the Multijet system recently developed by Fiat show just how fast this trend is going: a Fiat Auto Ireland staff member recently achieved 78mpg in a Punto powered by a 1.3-litre Multijet diesel.

Around the corner are engines that reduce the number of firing cylinders on low load (an idea that was a flop in the 70s because the mechanisms were mechanical, but can now be more easily and seamlessly done with electronics).

That last is more likely to have an impact in the US, which has a much higher proportion of engines with six cylinders and more than has Europe. GM is introducing such V8 engines in a number of cars for the coming model year.

If Americans could be persuaded to go the diesel route, there would be an even greater impact. But this looks unlikely unless there is a major Government policy shift from the cheap petrol regime which currently has that one country consuming around a third of the world's oil output.

According to forecasts by the Massachussetts Institute of Technology, global average car fuel consumption should drop by a third by 2020, and be down by half just ten years later.