We’ve got our fingers crossed for a high-powered hybrid luxury sedan.

The standard 2018 Mercedes-Benz S-Class can be had in a few different flavors here in the U.S. AMG and Maybach models excluded, buyers can pick up the V6-powered S450, or the V8-powered S560. Both options deliver gobs of performance – 362 and 463 horsepower (269 and 345 kilowatts) respectively – and come paired to an all-new nine-speed transmission.

In Europe, however, there’s even more variation. The S500 model in particular comes powered by a new M256 engine that’s paired to a 48-volt electric battery system. That powertrain allows for use of a few mild hybrid functions, as well as some starter-generator functions that help convert all of the Benzes belt-driven accessories to more efficient electric-driven accessories.

More Mercedes Spy Shots:

So, with that information in mind – why exactly is the German automaker testing a wide-body version of the hybrid luxury sedan? At this moment, we have no idea. But new spy video shows the wider, slightly meaner-looking Benz atop a transport truck with a few other unassuming S-Class models.

Our best guess is a slightly hotter AMG version. Maybe not a pure AMG model, but something akin to the AMG Line currently available on the S-Class. Added AMG accessories on the exterior, in the cabin, and even possibly some added performance in the engine bay. 

It’s the second strange prototype we’ve seen this week. Our spy photographers recently caught up with a Mercedes-Benz SLS AMG Coupe Electric Drive prototype testing on roads just outside the Nürburgring. Rumor has it that the prototype previews a high-powered electric motor for a fully electric supercar within the "EQ" range. Maybe this S500 will benefit from the trickle-down effect and gain a more powerful electric motor of its own.

Gallery: 2018 Mercedes-Benz S-Class

Got a tip for us? Email: tips@motor1.com