I have always wondered does the A/C on high use more gas than if it is set on the lowest setting? May be a dumb question but I still don't know the answer. I didn't know if the engine had to work harder to push the air or not if it's on high. People always say that the a/c uses more gas but I have never heard if there is a difference with the speed of the fan.

 

I want to say its using more gas, but not a signifigant amount more. Just a guess.

 

Its using more gas because it is working more to turn the compressor...all the compressor is doing when your NOT using your A/C is spinning. Once you turn on your A/C that pulley moves out just the slightest bit and takes away power from the engine...

More of a load on the engine, more gas being used....Think about driving on flat ground all day, compared to driving up a constant hill all day

-matt

 

Matt - I think he understands that the A/C in general causes more gas to be used, but he isn't sure if the blower motor speed, i.e. fan speed, affects gas usage (as a seperate issue from the A/C itself being on).

 

ohhh alright....my guess would be yea but very little difference...

 

Once the a/c kicks on it is mechanical draw. If you have the a/c on and high, that is just a fan setting, so it is just more electrical draw in addition. Having it on "high" will not theoretically use "more" gas. So if you are hot, turn it up, also, recyc is your friend on real hot days.

 

Now that you mention it, what is the difference b/n using recyc and not?

 

Recycle recirculates the already cool air, making it cooler theoretically.

 

It's not just theoretical, my car gets cool a lot quicker in recirc mode but it's not very healthy for you to breathe the same air over and over again.

 

Once the A/C is clicked on to any position it clicks on teh compressor, there the compressor sends teh freon around blah blah go read how it works, anyways, teh evaporator gets COLD and the air blows through it, now as you set each setting low or high all it does it change the fan speed.. Does not effect teh compressor..


So, in reality you are not wasting any more gas on 1 then you would on 4...

 

On Myth busters, they proved that it takes more gas to run the a.c. Under the same conditions( 5 gallons of gas, same load, 45 mph, 2 expeditions). the vehicle with the windows open went fifteen miles more than the one with the ac on.

 

 

and this is why mythbusters is awesome. so much useful info!

 

yea I saw that episode, I gotta watch it again but their first test was A/C winning over open windows, then they did the test different and windows open won (memory clouded).

 

In theory the aerodynamics of the vehicle change when the windows are open creating more drag causing you to use more fuel, not as much fuel with the a/c on I don't think.

 

mine takes 5mpg off.

 

the real question is at what speed (all other factors held constant) does the A/C win out? obviously it at some point above 45mph....

 

My Max's AC switch doesn't work on 1 , so having to use it at a higher fan speed, I use the thermostat more than most people I know

 

READ YOUR OWNERS MANUAL! ANYTHING ABOVE 60 MPH AT STEADY SPEED IS GONNA BENEFIT FROM WINDOWS UP BECAUSE OF LESS DAG AND WILL GET BETTER FUEL ECONOMY WITH AC.

 

whoa. calm down mang.

LAY OFF THE CAPS, TOO

 

ok guys how come when i'm doing 75 mph on a flat highway surface set in cruise control in 5th gear i put my maxima ac on full a/c #4 and with recirc and the rpm doesnt go up? then how is it using more gas, its not that i don't believe you i just want an explanation for the fact that supposedly there is more load on the engine? However, at idle when i put the a/c on there is a very noticable diff in rpm level. also for you guys that defend the recirc button how come most car manuals, like an 01 sentra's or 98 a4's to be specific tell you to use recirc only to get the air coming through the vents to cool the air quicker and then turn it off they claim it uses more gas than non-recirc? I also saw myth busters and we have to realize that our cars are more aerodynamic than expeditions and the diff. at 45 mph maybe less significant (i mean there are a lot of variables to say the least).

 

^ he has a point there. 15 mpg on a expedtion is like maybe could mean 30 mpg on a max. And 45mph.... who in here stays at 45mph..

 

That's retarded...

 

the rpms don't go up because the cruise control is regulating them to maintain the vehicle speed. to go a certain speed, you need a certain rpm level. the ac going on adds a load onto the enfine and the throttle has to be opebed just a little bit more. if you were sitting at idle and turn on the ac, you would see the rpms drop but the engine computer will then raise the rpms back up. you probably can't see the rpm drop at 75 because the engine is producing a lot more power then at idle so the drop in rpms is smaller and the computer compensates quickly. i don't know how the recirculate could use more gas because it is only air vent stuff. the only possibility i can think of is that you possibly could cause the evaporator to freeze over on a humid day and that puts an extra load on the compressor. that happened to my house ac, cost me $1800 for a new compressor.

 

That's true. You can also see that the windows resist being defogged when in recirc mode. Personally I'd use it in the event of chemical warfare or exit 12 on the NJTP, otherwise let fresh air in.

 

Thats a cool show, but that one was boring as crap. I like the one where they blew up the cement truck with 800lbs of commercial grade plastic explosive.

Anyway, It doesn't matter how much gas it uses, it's in the 90's here & not using the AC it crazy.

 

Is there any way to lower the temp below 65 degrees on the climate controlled ac system... it is hot as hell in Louisiana

 

The air that it is blowing is colder than 65. It will stop blowing as stong and cold until it reaches the desired temp. 65 degree air is not cold.

 

The fan speed on its own shouldn't make a difference, but the cooling load will. Our compressors work harder when more heat is transferred out of the cabin to the refrigerant. When the a/c is working hardest, it's therefore pumping more refrigerant and that will cost you more in terms of gas usage. When it is not working hard, the blower speed won't make any difference (except costing you through the alt).

 

I agree compressor is eather on or off it doesnt work harder.

 

you're retarded.

 

you are TEH

Fre·on


trademark
a trademark for any of a number of chemical compounds containing fluorine, and often chlorine or bromine. Use: as solvents, as aerosol propellants, in refrigeration.

 

R-134a DOES have flourine in it.
http://www.msc.navy.mil/n7/ein/038ein.htm

It does not contain Chlorine.

also... Here's another one for ya..
Fre·on ( P ) Pronunciation Key (frn)
A trademark used for a variety of nonflammable gaseous or liquid fluorinated hydrocarbons employed primarily as working fluids in refrigeration and air conditioning and as aerosol propellants.

 

Man, it was 101 degrees outside today. I would have DIED without that shiet.

 

hehe, i love the sfmg