AC question!!! Which saves more gas?!?!
 

So...
I probably been thinking about this topic for last couple of years...
But the way I use the air condition in my car is always been the same...
I only use AC during summer and never use it during winter...

But if I use the AC, I always put it to the coldest setting and turn it to the lowest level. If I get cold in between I turn off the AC. Then if I get hot again I turn it to the lowest level. Back and forth... So like on a long drive, I would turn it on and off quite few times... Now does this save gas compare to leaving the AC on all the time but adjusting the temperature? Of course level being set to the lowest level.

Anyone know this? I googled enough and wasn't really lucky with it... lol...

Thanks for reading guys =)

I don't know for sure I am guessing it does (save gas/energy). I usually do the same as you though although I typically don't have to turn it off very often.

Lately I have found myself turning the A/C on even when its pretty damn cold out simply because its too humid out. Seems like its been more humid than usual this summer.

on all the time, coldest seting and nob is at 2 oclock position

Same here...I use the A/C all the time in the same fashion since I live in a tropical climate...The only weather we have here is Sunny or Rainy...so U need the A/C pretty much of the time...and a full tank of Gas usually lasts me about two weeks.

I also heard that the Z has a sensor that will turn off the compressor of the A/C wen u get on the gas/throttle...Does anyone know if there's any truth to this?

only time i use the a/c is if im on long road trips on the highway and if its really hot. The Z didnt have a huge issue buy my Evo does. Damn thing nearly stalls at when im at a light with the a/c on...thing sucks so much power from the car its unreal.

If cycling your AC on and off manually saves gas, it's just because you're making the average temperature higher than it would be if you left it on all the time at the coldest setting. In any case, even on older cars the A/C compressor cycles on and off while you have it "on". It's just part of how the whole system operates.

The A/C in the Z is thermostat controlled anyways. IMHO, set all the dials to "Auto" and set the temperature at your comfort vs cost limit. The colder you set the dial, the more gas you'll suck over time. It will be far less trouble and just about as effective.

A related issue that's been debunked before: rolling down the window vs running the A/C. Assuming you can bear the heat level of running with the windows down and no A/C to save gas, it actually does save gas at low speeds (city streets). However, on the highway, the parasitic drag on the car from having the windows open wastes more gas the running the A/C, so don't do that.

I keep it on during the Summer at a comfortable setting.

So true, I wish people would understand this. I swear I always run into people saying ac uses more gas no matter what. Either you understand physics or you don't I guess.

This sounds completely false to me but I don't have any scientific data to back that claim up. :ugh2:

gut reaction: let the Auto modes do the work. Turing your car into an icebox 3 times on a trip then letting it heat up seems much more wasteful than just letting it settle into 75 and staying there.

however, the cabin is pretty small compared to most cars, so it is probably cheap anyhow to cool it off.

hard for me to tell since i just go with the top off everywhere.

It's more of a fluids question...

...but at 70 or so, most cars use about 2.5% more gas with the windows down, and 5% more with AC on, so.....:ugh2:

Mythbusters tested this (measuring fuel consumption and efficiency in real cars), and then went back and revisited the issue after comments and concerns and re-tested. Wikipedia's final summary of their final summary:


ETA: It's probably a reasonable assumption that the 50mph figure will vary depending on the aerodynamic configuration of the car and the windows, as well as other differences affecting the A/C compressor's efficiency. But it's a reasonable ballpark, and reasonable cars' break-even point probably doesn't vary a whole lot.

really, worrying about the ac on a 3.7l?

Great post, very informative!

OP, I do the same thing as you and the difference is barely noticeable.

Unfortunately, it still kinda sucks about the whole windows thing.

I mean, if you're on the freeway, you'd use AC because of parasitic drag. When on the street, you use AC on a warm day because windows do nothing but stay the same with ambient temperature at the stop.

Or if you're a baller, you can roll your windows down to enjoy the fresh air while blasting your A/C at the same time to keep cool.

If you're a super-baller you can drive a Convertible Z with the top & windows down and the A/C blasting :icon17:

Hard to believe you bought a Z and are worrying this much over fuel consumption with the AC on.

:iagree:


This is the same issue as if you put your tailgate down on your truck to save gas...

I try my hardest not to use the A/C unless I really have to or have a passenger in the car. One trick you can use is if you really need the A/C, try lowering one of the windows slightly. This creates a negative pressure area that actually draws air out of the car which in turn pulls more air through the air con system.

It adds the same amount of extra air as using one additional fan speed, not bad! The higher the fan speed, the more current the system is drawing which means more load on the engine.

I'm pretty sure all cars now do this above a predetermined level of throttle.

i recommend you use it in the winter in defrost mode too cause the quickest way to kill a/c is not to cycle it regulary while the car is on.. imho. :)

i just keep my hvac in auto mode all the time. even in the summer i drive with the window open on the driver side and hvac blowing. im rather spoiled and enjoy my cars that way. :p

This is what I do :tup:

I really like driving with my windows down atleast half way...only AC if I feel like I'm overheating or sweating up my fine linens

It also bugs me that I am heating up air that I just cooled.

yea I know, some you guys are going to dog me for buying a $30k car and worrying about these little things, but its not like I;m not making it rain out my back window with dollar bills from my $30k car.

OK, I guess I'll have to dog you about it.

Personally I bought my Z because it's enjoyable to drive. If I was concerned about mileage I'd have bought a Prius. I certainly wouldn’t have bought a car that required premium fuel. When I’m driving the Z I think to myself “man I wish the Z had…” WAIT, NO! I like it just the way it is! The Z is about enjoying the driving experience. So I’ll set the inside temp to what’s pleasurable and if I get 0.5 mpg less I don’t give a rats *** because I’m having a great time enjoying the car and the road.

Geeze, just dump in another $70 of 93 octane and enjoy it some more. :driving:

No one still answered my question... which is betta? anyone know? lol

Sorry JNZx I know this doesn't answer your question but I just want to say I'm doing the same. I Love the feeling of fresh air and only use A/C sparingly when it gets way too hot. Otherwise I would turn the A/C on to cool down the cabin so my long trips would result in turning it on/off multiple times.

:iagree:

THat's what ATC is for. It does it for you so you don't have to do it

Oh I have no problem driving the car, and said nothing about extra $$ to air condition. I, just like the OP leave the AC on the lowest (coldest) setting, but unlike the OP I dont turn it off. (turning it off sets the recirc back to 'fresh' which is not good on humid days) In fact, even in your example, Prius' heat the cooled air the same way.

You are using the compressor to cool the air then to warm it back up before it comes into the cabin. Even in multi-million dollar homes the HVAC units dont heat up the cooled air.

With the seat coolers on full as well! :)