What is the car model with the highest mpg ?
select t1.model from car_names as t1 join cars_data as t2 on t1.makeid  =  t2.id order by t2.mpg desc limit 1;
select t1.model from car_names as t1 join cars_data as t2 on t1.makeid  =  t2.id order by t2.mpg desc limit 1;
[{'Model': 'citroen'}]