THREE is becoming the magic number for manufacturers striving to produce cars which use just three litres of fuel per 100 kilometres. At the Frankfurt International Motor Show a number of manufacturers, including Audi, Volkswagen, SEAT, Nissan, Vauxhall and Daihatsu, rolled out plans for 'three-litre' cars, which can achieve just short of 100mpg - with diesel engines offering the holy grail of performance and economy rolled into one.

The reliance on diesel will send a clear signal to the British Government that its plans to penalise diesel with a 3% premium over petrol vehicles under the new company car tax system does not recognise the vast improvements in emissions available by using the fuel. The fuel economy milestone is seen as a key achievement to provide a 'green' halo effect by manufacturers for the rest of the car range and prove their technological prowess.

But diesel is not the only option, as Vauxhall was also in the running with its G90 concept car, so called because it produces 90 grams of CO2 per kilometre from its three cylinder 1.0-litre direct injection petrol engine, which achieves 3.88litres per 100km.