Does Airconditioning waste petrol?

[VjamesY]

The other day a friends Dad (tight ass) mentioned to me that using air conditioning can waste heaps of petrol = money.

Not like I'm worrying or anything, even caring for that matter. But the other day coming home from work I was stressing out because I was very low on fuel and about to run out, so I decided to turn the aircon off even though it was a stinking hot day.

i didn't think it would make much of a difference, share your thoughts?

[Stressball]

i wouldnt say its wasted, if its hot its totally worth it

It does. More drain on the alternator = more drain on engine needed to keep everything powered and running etc

[Grennan]

I wouldnt say HEAPS. Certainly not enough to get all penny pinchy over. I certainly havent noticed any noticeable difference in fuel consumption over the last few weeks where Ive been using the air con.

[Stressball]

I wouldnt say HEAPS. Certainly not enough to get all penny pinchy over. I certainly havent noticed any noticeable difference in fuel consumption over the last few weeks where Ive been using the air con.

I did when we got into winter last, but that may not have been that i was using A/C less, and more than the air was denser so less provocation needed to get the car going.

[Philthy]

7% is a figure I've heard thrown around a bit. Supposedly 7% more fuel with the AC on. Its a noticable difference for mine on the highway

[Escape-The-Fate]

i'd say yes to my vz, i tend to try not turn it on unless stinking hot...something to do with the fact its 175, automatic slug and the aircon puts more of a strain on the engine so kinda feels slower aswell.

[spark79]

im a mechanic, it dosent strain the engine, using the air cond is equivilant to having one extra passenger in your car, if you drove an old skool car with a piston type compressor yes it does drain power and use fuel, but most newer cars use a rotary vain compressor wich is very effecient!!!

[axemurderer101]

pretty sure mythbusters tested this, i cant remember what the figures were but they tested fuel mileage with aircon on vs windows down vs windows up and air con off

[Jezza]

well i think top gear say it takes about 15% of the cars power but thats just the SIARPC vehicle

[minux]

Just a little off topic, after owning fords, holdens and now subaru's, i can without a doubt say Holdens seem to drain massive power when aircon is running, the Xr8 and XR6 i had one lease, when aircon on wasnt really a change in how the car drove, in the senator, AMAZING difference in power output, so much so that if your doing 60 and click on aircon, you feel the car labour for a second. The Subi, can notice it a little off boost, but it would be expected in a little 2.5 4 banger.

I would suspect seeing this sort of drain in the holden that it would increase fuel consumption quite a bit moreso in traffic.

[Lumps of cheese]

Meh, turn it off and put the window down, better than plastic air anyday

[redrags]

if you run your heater i believe it does the opposite because something to do with the thermo and also your water temp goes down anyone got any idea of this?

[thedeadwalk]

it would be colse to the same as haveing the windows down you know with the drag.
so to re-cap when its 45c have all the windows up and no air-con on.
save fuel and give the car a few pounds of sweat as well

[0081]

Yes using the AC will use more power, you are using the motor to turn a pump that will suck power which ever way you look at it you will use more fuel.

The higher you rev the motor the more you will be able to tell, you can also hear the difference( in my car at least you can)

[Full Spectrum]

At cruising speeds it should not use anymore. But idle stop start, That is a different story. But who cares when it is 40deg.

[Grennan]

Yeah the air con in my car kicks ****ing arse. Im tempted to just cruise around the freeway on a loop in summer.

[Michael_123]

Cant say i notice a difference in my car re power wise.

[mz81vs]

When i had my VZ i definitely noticed it used more fuel and slight loss of power. Haven't really used the air con with the VS so dunno yet.

[TMM]

well i think top gear say it takes about 15% of the cars power but thats just the SIARPC vehicle

In most cars under full throttle the AC turns off, so it's a moot point.

[Cheap6]

The read out on my scan gauge shows fuel consumption at idle rising by ~0.3L/hour when the A/C compressor engages. Of course the compressor is not engaged continuously. There might be some small differences from that value depending on ambient temp., which changes the work the compressor must do (as distinct from its duty cycle), and higher (compressor) rpm, also increasing the work, but reducing the duty cycle.

If you can be bothered, only switching the A/C on when decelerating can recover some kinetic energy and reduce the FC penalty. You might find that reduces the time spent with fuel cut out on decel. though.

There is a recent article in an online magazine that uses a throttle position switch to switch the A/C compressor off at larger throttle openings (<100%), going part way to doing the same thing, and helping to average the load on a spark ignition engine thus increasing the time spent operating at (more) efficient loads.

Using (some) recirculated ventilation air rather than fresh will reduce the work the A/C system has to do.

Tinted windows will help also. Many (all?) new cars have glass coated so as to block at least some of the Solar radiation of wavelengths that heat a car interior.

[Cheap6]

Just a little off topic, after owning fords, holdens and now subaru's, i can without a doubt say Holdens seem to drain massive power when aircon is running, the Xr8 and XR6 i had one lease, when aircon on wasnt really a change in how the car drove, in the senator, AMAZING difference in power output, so much so that if your doing 60 and click on aircon, you feel the car labour for a second. The Subi, can notice it a little off boost, but it would be expected in a little 2.5 4 banger.

I would suspect seeing this sort of drain in the holden that it would increase fuel consumption quite a bit moreso in traffic.

How noticeable it is might just be down to how effectively the engine management can throw extra air in when the compressor engages. Should be virtually unoticeable with DBW throttle.

Also, forgot: The engine cooling fan will be on with the A/C compressor engaged. That will be worth 80W / alternator efficiency (~60%). To put that in perspective, I have seen quoted average power, measured in an urban driving environment, 1500kg car, of 6kW.