Stock Photo: A Chevrolet Volt hybrid gas/electric car is on exhibit in Embarcadero Center in downtown San Francisco It is the most fuel-efficient car with an internal combustion engine sold in the United States and can travel 25 to 50 miles on a lithium-ion battery w. A Chevrolet Volt hybrid gas/electric car is on exhibit in Embarcadero Center in downtown San Francisco It is the most fuel-efficient car with an internal combustion engine sold in the United States and can travel 25 to 50 miles on a lithium-i