2015 Volkswagen Golf TSI, front three-quarter view.

In 2007, the European Union mandated fleet average CO2 emissions of 158.7 g/km. For 2015, that figure will drop to 130 g/km, and the target for 2020 is an ambitions 95 g/km. Thanks to some German politicking, that target will be phased in from 2020 to 2024, but it will still apply to 80 percent of passenger cars in that first year. In US miles per gallon, that's the equivalent of going from about 35 mpg to 42 mpg to 57 mpg. The current Volkswagen Golf is rated from 85 g/km of CO2 to 190 g/km depending on model – and zero for the e-Golf, so for the next-generation MkVIII hatch due in 2019, to meet the goal, Volkswagen engineers will need to introduce a bunch of new tricks. According to a report in Autocar, VW be mining its hyper-efficient XL1 for some of them.

Predictions for the next Golf include a variable-compression engine, an electric flywheel and an electric turbo, along with taking greater advantage of coasting. Volkswagen could be getting help from Audi with the electric turbo and variable-compression engine and electric turbo, with Audi already having shown off the former and brand technical boss Ulrich Hackenberg confirming the VW Group is working on the latter. It's possible the flywheel system could also have the mark of The Four Rings: Autocar mentions a British system that Volvo is testing, but the R18 e-tron Quattro racer has been using one for years.

The need for such features is because the company won't be able to net enough future gains from just aerodynamic improvements and advanced materials. As price will be a factor (the regulations are expected to "add hundreds of euros to the cost of building a car"), adding much more aluminum or carbon fiber is an unlikely option. We're told the next generation won't be longer or wider than the current car, and being Europe's most popular model, VW doesn't want to make a big bet on futuristic aero, but the report says the MkVIII will "likely" have "the most aerodynamic treatment yet seen on a production vehicle," the area where lessons learned from the XL1 will truly be seen.