Does a car consume more up and downhill (equal distance) then on a flat road at constant speed ?

Question

If you drive the same distance uphill and downhill at constant speed and the same slope do you consume more gas then if you would drive the same distance at same speed on a flat road?

Answer 1

On the uphill the car uses the most. Now you would think on the downhill the car would use the least but the engine must keep up with the speed of the car. Therefore it is possible for the car to use more fuel than necessary when going downhill. It would use the least fuel going downhill and in neutral.
As for when on flat road at a constant speed the vehicle is usually most fuel efficient.

Answer 2

uphill would consume more gas because the engine needs to run with the load of going up and you would have to keep your foot on the gas pedal to stay moving up and not start going backwards (assuming it is a steep slope). down hill would consume much less because the engine does not need to move the vehicle, gravity alone will let it go down. you can turn off your engine and keep your foot on the break and your car would still go down (neutral gear). but on a horizontal or flat road the car would consume more or less gas depending on the fuel efficiency rating of the car. say your car has about 25 miles per gallon rating: uphill it will consume more, probably end up about 20 mpg or so. downhill would be less, so efficiency would be around 30 mpg. on a regular flat road it would stick to the rating, more or less 25, say 24 or 26 depending on how often and hard you accelerate.

Answer 3

Yes, the uphill travel needs more power and the downhill (coasting) does not make up any significant difference. Once a car has reached speed it consumes less fuel than needed to overcome inertia.

Answer 4

A car requires more gas to go uphill and (assuming you don't deliberately accelerate) needs less gas going downhill