Drum roll please… of the Best Gas Mileage Cars on the market, the Toyota Prius comes up on top once again. This gas sipper gets and EPA average of 51 miles per gallon in the city and 48 miles per gallon on the highway. How does it get such good fuel ratings you might ask? Well, the Toyota hybrid system is electric based first and then the gas engine kicks in. At slow speeds, if you drive it right, the Prius can drive on only electric. Obviously when you do this, you are not spending any gas and you can achieve that awesome rating.