Europe's CO2-based taxation system means consumers already have access to a wide range of highly efficient vehicles.

There are stricter targets on the horizon however, and Renault is the latest to accept a challenge set by the French government to produce a 117 mpg car by 2020.

According to Autocar, the French automaker will show off a 117 mpg concept vehicle at the Paris Auto Show in October.

Renault's design boss Laurens van den Acker says the new vehicle is "a really interesting concept", but that it isn't based on an existing Renault platform.

The reason for this is weight. While Renault's current lineup is hardly overweight, none have the kind of technology that will be required to hit future fuel economy goals.

And as a recent survey shows, reducing weight is currently the number one priority for automotive engineers and designers.

To achieve the kind of numbers Renault is promising from its concept, says van den Acker, "you need a dramatic weight reduction and a dramatic aerodynamic improvement."

It isn't clear what form Renault's concept will take, but van den Acker says it will combine regular hatchback, crossover and sports car styling cues.

If the French government's 117 mpg target seems arbitrary, it makes more sense when converting back to the European fuel economy measurement of liters per 100 km.

117 mpg equates to 2 liters of fuel per 100 km. For reference, Volkswagen's XL1 plug-in hybrid is considered a '1 liter car', capable of beating 1L /100km--its 261 mpg rating is actually just 0.9L /100km.

Renault's French rival Peugeot has also experimented with new technology to try and reach the French target--notably with the 208 FE concept: a lightweight, three-cylinder hybridized take on its 208 subcompact. Its claimed MPG was--perhaps unsurprisingly--also 117 mpg.

This year's Paris Auto Show kicks off on October 2, 2014.


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