Why do cars average a higher mpg on highways than in the city?

Question

Why do cars average a higher mpg on highways than in the city?

In: Engineering

Answer 1

Depends on the car. At higher speeds it takes more energy to drive (need to push the air out of the way). At low speeds it takes much less. However in city driving you use the brakes frequently, and brakes convert energy to heat and throw it away (wasting fuel). Highway driving doesn’t use much brakes.

Second, when stopped your car still runs and uses gas. So waiting at a light is 0MPG. Also accelerating requires the engine runs through the inefficient speeds.

Hybrids and EVs change this, they don’t use gas when stopped and they don’t use brakes to stop (they have regenerative brakes), so the difference between highway and city is higher speeds need more energy to push the air which means they get better city MPG.