There is more than one significant factor. How you take off, how fast you drive, keeping your tires inflated to the correct PSI, keeping the car tuned up, and the conditions where you drive, be it city, highway, or a combination.
Demand
taxation.
NO
the answer to that question is our cars and littering
check here http://www.wonderhowto.com/how-to-calculate-cars-fuel-efficiency-mpg-084812/
Their shape and aerodynamic efficiency makes them streamlined.
Static and Kinetic :)
Wacking cars is the answer to most things. Wacking cars makes you get happy. Wacking cars like a Wacker-a-car-er is the answer. Wack Cars.
he used a conveyor belt for the model t cars
Apples, cars, sunglasses... It depends on what you mean, significant.
making cars that get better gas mileage
making cars that get better gas mileage