Until now. You see, in 2012, Europe will have new CO2 legislations, which will require each car manufacturer to have an average emission rating of 120 g/ km for their entire range. The target, according to most manufacturers, is unrealistic, but they have to meet the deadline, before they start paying heavy penalties.

This means that big-engined supercars will have to clean up their act. Audi did just that at the Detroit Motor Show and, along with Koenigsegg, seem to be paving the path for a new generation of European supercars that will find themselves not burning gasoline.

The Audi R8 has been a showcase for the Ingolstadt-based manufacturer's engineering prowess. Now, with the V12 TDI, they've made the case for a diesel supercar. Using the same engine block from the Q7 V12 TDI, the R8 TDI becomes the first production diesel supercar in the world.

Producing an astonishing 490 bhp and 101 kgm of torque, the R8 TDI can out-accelerate its own petrol sibling to 100 kph, registering a time of 4.2 seconds, vis-�-vis 4.6 seconds.

This is due to the fact that all its torque is available from a mere 1750 rpm � truly locomotive like. Audi claims a top speed of 300 kph, which puts it in the same league as other supercars.

But performance apart, Audi have pulled the rug from under everyone's feet by making it Euro-VI ready, a stricture that is slated to be in place as late as 2014. It does so by the use of common-rail direct injection that features piezo injectors, twin particulate filters and an aqueous urea solution tank.

Now, it won't leave behind a bad smell, since the system is perfectly sealed from the environment and the passenger cabin, but the solution itself is exposed to exhaust gases.

These in turn convert it into ammonia, which splits the nitric oxides into inert nitrogen and water. Audi claims that the system remains effective for the service life of the vehicle.

If Audi believes in an aluminium construction body for its R8 to enhance efficiency, Koenigsegg believes its new CCXR deserves a diet of carbon fibre. Only six of these ultra-fast bio flexi-fuel cars will be built.

At 1018 bhp, they are more than twice as powerful as the R8 TDI and can demolish the 0-100 kph run in 2.9 seconds, carrying the car all the way to a top speed of 417 kph. Priced at nearly US $200,000 over the most expensive production car, the Veyron, the owner pays a very high price for going green.

But going green has its benefits. This car runs on E85, a mixture of 85 per cent ethanol and 15 per cent petrol. It is prepared from corn crop and generally has a higher octane rating of 100 to 105 RON, compared to gasoline, which is in the 87-98 RON range. By the use of E85, the company hopes  maintain the performance of its vehicles through newer technologies and energy sources.

So one fine day, will it be incorrect to ask an enthusiast if petrol courses through his veins? With the emergence of newer technologies, it looks like the days of gasoline-driven supercars might be numbered.