I'm looking at a 2014 Toyota Prius Four, and am wondering if it is plug in or not? Is it nickel based battery or lithium based? Also, what is there to watch out for when looking at one? How do I tell if the hybrid battery is bad? How do I tell if it's burning oil? Is $11k a bad price? Also, why are some priced $6k and others $15k or more? Are the 6k ones basically guaranteed to require a battery swap/timing chain replacement? Or is there more to the story? Or does it have to do with engine setup/VVT-i? Is it the intake or the exhaust that gets clogged up? I'm getting conflicting reports from reviews. How much different are the cars in this gen? Someone mentioned that they had ironed out most all the kinks in the 2014, but what about the 2015?