The sixth-generation Hyundai Sonata (codename YF) marked a radical turning point for the brand thanks to its bold "Fluidic Sculpture" design. Focus on the Hybrid version: Introduced in 2011, the Sonata Hybrid was Hyundai's first mass-produced hybrid vehicle. Unlike Toyota, which uses an e-CVT transmission, Hyundai opted for a traditional 6-speed automatic gearbox coupled with an electric motor and a Lithium-Polymer battery (lighter and more compact than the NiMH of the time). Overall reliability note: The reputation of this generation is heavily tarnished by the Theta II GDI (direct injection) engine scandal in North America, prone to premature failures and fire risks. However, the Hybrid version uses an indirect injection (MPI) Atkinson cycle version, which spares it from the worst defect
Buying a YF generation Hyundai Sonata (2010-2014) is a minefield. If you are targeting the 2.4 GDI or 2.0T GDI versions, walk away: the risk of engine failure or fire is statistically too high, unless the engine has been recently replaced by Hyundai and comes with a transferable warranty. Regarding the Hybrid version (your target): the verdict is more nuanced. It uses the 2.4 MPI engine (indirect injection), which saves it from the disaster of the GDI engines. Paradoxically, it is the safest version in the North American lineup. However, this is the first generation of Hyundai's hybrid system: expect sometimes brutal transitions between electric and combustion, and keep in mind that a high-voltage battery replacement on a vehicle of this age will cost more than the value of the car. Buy only with a crystal-clear maintenance history and after checking the condition of the battery.