Human: I'm looking to buy a new car. What are the most fuel efficient vehicles? Assistant: 
The most fuel-efficient vehicles on the market today are hybrids, electric cars, and hydrogen fuel cell vehicles. Hybrid cars combine a traditional internal combustion engine with an electric motor, which helps reduce fuel consumption and emissions. Electric cars use electricity stored in batteries to power their motors, resulting in fewer emissions than petrol or diesel engines. Hydrogen fuel cell vehicles produce electricity through a chemical reaction between hydrogen and oxygen, making them even more efficient than electric cars as they require no gasoline or other fossil fuels.