its it true that when u use your ac while driving u waste more gas??

Question

i know it doesnt but i wanna proof it to some of my relatives and friends that its not true

so if u engine is running harder and spinning the belt fast shouldnt ur speed increase too because of this? i use mine all the time and i dont a difference in gas. two times i drove to vegas from los angeles once with the ac on an once with off during the same time of day and weather and speed and was the the same. does this means some cars do and some dont?? my car is 95 accord lx 4 cyl non-vtec 4 door

Answer 1

On the highway it will be less apparent...

When the car is idling and the ac is on the car must work a little harder..(more load)

In other words when your car is idling it isn't using much gas but it is also not producing much power...The little change of the ac adds to the friction factor and in turn becomes less efficient.

When on the highway the car is working to keep the speed over 55 so the minute difference is less apparent...

If you remove 1 out of 10 that is 10% (iddle)

If you remove 1 out of 100 that is 1% (reving 3000rpm)

It still uses (1) unit of load but it has less effect the more the engine produces power...

The kicker is this... let's say your car could iddle for 10 hrs without running out of Gas and without the AC on... That means that with the AC on the car would work harder and in turn run out of gas first.

Does a passenger make your vehicle less efficient? The extra weight is friction but is not apparent when the car is maintaining it's speed...

Good luck explaining it,

Answer 2

It is mostly true. Anything that makes the engine work harder will burn more gas. But driving with the windows open creates atmospheric drag, and the mileage penalty is about the same as the AC on and the windows closed according to the TV show Mythbusters.
Best MPG is AC off and windows closed weather permitting. Keep the fan on, but the AC off.

Answer 3

The reason that the mileage was the same without the AC is that you had the windows down. That increases wind resistance, and burns as much fuel as the AC being engaged. You might see a difference if you drove with the windows closed the whole way, but on this sort of drive (hot weather) it's virtually impossible to survive.

Answer 4

If you really want to find the truth about this, buy a scangauge from ebay and plug it into your car. Find a level road and set the cruise to hold 55mph with the a/c off. Note the engine load and MPG readouts, then turn on the a/c. You will immediately see that the engine load will increase and the MPG's will go down.
You are totally wrong in your assumption that using a/c doesn't decrease the miles per gallon.

Answer 5

Sorry but your relatives are correct.

It is true. Running the A/C burns more gas and takes power away from the engine.

The A/C compressor is belt driven, meaning that the engine must not only push the car and the other gadgets running off the belt but also the A/C compressor.

it can not only cost you more in gas but it also robbs quite a bit of horsepower from the engine.

Answer 6

Yes, definetly. I used to have a small car in which I had to turn the ac off to be able to accelerate enough to pass another car. I always turn the ac off if I'm about to run out of gas.

Answer 7

Im sorry, but yes, your relatives are correct.

Turning the A/C in while driving can affect your gas mileage because it also uses the engine, causing it to burn more fuel.

Answer 8

Of course, more load = more fuel consumption,
BUT some-one, (wish I remembered who), did an actual test, and the difference was miniscule,
( in the 1 MPG range for a vehicle getting low 30s
IIRC).