Mercedes-Benz has a new plug-in hybrid sedan hitting the market in 2015- the S550 Plug-In Hybrid. Here’s what you need to know: 1.)  The S550 Plug-In Hybrid is the first Mercedes plug-in hybrid vehicle in the US but not the automaker’s first hybrid vehicle- that was the 2010 S400. 2.)  F1 technology was infused in the design of the S550 Plug-In Hybrid