Why is there such a big difference in city and hiway gas mileage?

Question

Why is there such a big difference in city and hiway gas mileage?

Answer 1

bc in city driving you have to stop and go all the time, but on the highway you get a onger ride at the same rpms and it saves your gas

Answer 2

Because of the stopping and starting.  You use much more gas to accelerate than to just maintain a constant speed.

Answer 3

Because you use more gas when you accelerate.  When you are on the interstate on trips or something, that's why you get better gas mileage, because you're not constantly breaking at red lights, etc. and then speeding back up.

Answer 4

in the city you stop and go all the time

Answer 5

It burns more fuel to accelerate than to maintain a constant speed, you also spend more time idling in traffic, and it may take you 20 minutes to go a couple of miles, where as on the highway you will go 20 miles in the same amount of time if you're driving a constant 60mph. Highway gas mileage isn't referring to being stuck in a traffic jam on the highway, your gas mileage during this time is more reflective of city mpg.

Answer 6

City MPG is always lower than highway MPG because in city or similar traffic, stopping is much more frequent along with frequent changes in speed.  On top of that, vehicles consume more fuel in 1st and 2nd gear than any other, and those gears are not used on the highway (except for in traffic, in which case you'd refer to the City MPG.)

The reason that stopping and subsequently re-accelerating takes more gas is because the engine has to start moving from nowhere.  Think about how heavy a car is, and imagine it is at a stop-sign.  When the car starts moving again, the engine has to start with no momentum since it's not moving, so more fuel needs to be used to get the car moving.

When you're on the highway, there are much less situations where you need to get your car moving from a stopped position-- therefore, saving gas.  You've also got quite the momentum going on the highway since speeds are much higher-- helping out the engine when it comes to making the car move.