As the Geneva Motor Show finally closes its doors to the public, many will go home lusting after the LaFerrari or McLaren's P1 hypercars.

For others though, the show's indisputed star was the production Volkswagen XL1--as thoroughly engineered to be economical as the others are to be fast.

While VW hasn't yet revealed pricing for the ultra-frugal XL1, it's expected to be high. Happily, we may still see some of its technology in more affordable models.

Autocar reveals the XL1's powertrain engineering is to be scaled up for future plug-in hybrid cars, on the Volkswagen Group's MQB platform.

That's the vehicle architecture found under the new Volkswagen Golf, and will also be the basis of dozens of other VW Group models in the coming years. That includes the Audi A3 e-Tron plug-in hybrid, also unveiled at Geneva.

Rather than the diesel of the XL1, the e-Tron features a 1.4-liter turbocharged gasoline engine, paired with a 75 kilowatt electric motor. On the European economy cycle it's a combination good enough for over 150 mpg, despite 138 mph performance. A Volkswagen Golf 'Twin Drive' hybrid follows, and will share the Audi's strong performance and economy.

It may be a while before VW releases a production vehicle using the XL1's carbon-fiber body shell technology, mainly on cost grounds--but another of its stand-out features may become popular: virtual door mirrors.

The XL1 is the first car in Europe to gain permission to dispense with regular door mirrors. Instead, it uses two rear-facing cameras, the views of which are displayed on small screens inside the doors.

VW says the view is actually better than that of regular mirrors, because it covers a wider angle.

Now that the system has gained approval for use in the EU, it's only a matter of time before other cars follow suit.


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