<human>:  Which types of cars have the best fuel economy?
<bot>: The most fuel-efficient cars are typically hybrid and electric vehicles. Hybrid cars combine a gasoline engine with an electric motor and battery, while electric vehicles primarily use an electric motor and battery. Plug-in hybrids offer the flexibility of using a backup gasoline engine when battery power runs out. Among the hybrids, the Toyota Prius is one of the most well-known models, while the Nissan Leaf is a popular choice among electric vehicles.