Question: what are the top fuel efficient cars?
Answer: Hyundai Ioniq. Our pick Hyundai Ioniq Plug-in Hybrid. Fuel economy 247.8mpg. CO2 26g/km. Latest Hyundai Ioniq deals from £12,499. ... 
Toyota Prius. Our pick Toyota Prius Plug-in Hybrid. Fuel economy 235mpg. CO2 28g/km. Latest Toyota Prius deals from £15,500. ... 
Kia Niro. Our pick Kia Niro. Fuel economy 201.8mpg. CO2 31g/km.