PARIS – Pressure to reduce fuel consumption has persuaded Peugeot Automobiles to design future models that are lighter than their predecessors.

The move is an about face from current industry trends.

“Tomorrow, the reduction of mass will be much more important,” says Bruno de Guibert, Peugeot’s director of product and markets. “We will keep improving motors and reducing friction, but weight is the most important factor in fuel consumption in urban driving.”

De Guibert says future Peugeot models in Western Europe cannot give up safety features or interior size for weight reduction, but the exterior dimensions could be reduced and components made lighter.

“We have made a lot of progress on designing parts” that use less material, he says, and lighter materials can be substituted for heavier ones. Future Peugeot fenders could be made of plastic, for example.

Up to now, the European auto industry has tended to let individual models grow between generations until they reach a higher market segment, at which time a new small car is introduced.

The fifth-generation Volkswagen Golf is 2 ins. (5.0 cm) longer and about 221 lbs. (100 kg) heavier than the version it replaced, while the Peugeot 207 grew 8 ins. (20 cm) and weighs 341 lbs. (155 kg) more than the 206.

“There will be an inversion of this trend,” de Guibert says, noting Mercedes-Benz already has started the reverse trend with its current S-Class, which is lighter than its predecessor.

Legerity was a key theme of Peugeot’s recent fourth Concours de Design competition won by a 20-year-old Romanian design student. The Flux roadster he designed is conceived to use a lot of aluminum and carbon fiber, and its forms are thin and airy.

“Our specifications for future cars will be to reduce their weight, lightening the vehicles while integrating all the demands of consumers,” Gerard Welter, chief Peugeot designer, says.

For years, it appeared carbon dioxide emissions of 120 g/km – the equivalent of 46 mpg (5 L/100 km) with a gasoline engine or 52 mpg (4.5 L/100 km.) with diesel – would be the European Union’s next emissions goal, but Germany lobbied heavily against that target, saying it would hurt the German economy.

So the EU recently agreed new-car fleets in 2012 must emit an average 130 g/km of CO2. The European and Japanese auto industry have agreed to a voluntary goal of 140 g/km in 2008, but Europe will fall short, mainly because the German luxury makers are not close.

The EU has not yet decided what penalties it will impose for missing the 130 g/km target, so not every auto maker has chosen the 2012 fuel-efficiency strategy.

BMW AG, for example, regularly pays fines in the U.S. for failing to meet corporate average fuel economy standards – a record $42 million in 2003, but it still earns more selling big engines than it has to pay.

PSA Peugeot Citroen, however, is aiming at full compliance, and both brands will benefit from the reduced weight of their shared platforms. Frederic Saint-Geours, Peugeot general manager, says the auto maker already sells 20.6% of all vehicles emitting less than 120 g/km.

Although parent PSA is developing hybrid-electric diesel drive systems, de Guibert does not expect hybrids to contribute very much to CO2 reduction.

“Hybrids will develop slowly,” he says. “They continue to have a problem of price. Any major rupture of technology toward hybrids or fuel cells will only arrive with government intervention, taxes on fuel or CO2.

“Today, the diesel is the most economic solution for reducing fuel consumption.”