Mercedes-Benz C-Class PHEV

Testing appears to be underway for what would be the first Mercedes-Benz C-Class with a hybrid powertrain. We can see a pair of the prototypes undergoing testing in Germany, with one, a C-Class Wagon, still heavily clad in camouflage and featuring a more noticeable outlet on the passenger side of its rear bumper.

There's also a more production-looking sedan, which features a not-so-discreet flap over its rear-bumper outlet. It's difficult to speculate on power outputs for this fuel-sipping C-Class, although our spies seem to think that this car will feature some combination of a four-cylinder gas engine with an electric motor, although just which four is unclear (note, we wouldn't mind if MB fit its 2.0-liter turbo with some batteries and motors). Regardless, the four-pot/electric motor seems like a pretty reasonable combo, although it probably means that Mercedes won't be challenging the six-cylinder-powered system of the BMW ActiveHybrid3 any time soon.

When the plug-in C-Class arrives later this year as a 2015 model, it will likely offer a full range of driving modes, including both gas or electric, only, as well as a more traditional hybrid mode.

Take a look up top for our gallery of spy images of this ultra-efficient Mercedes.