I know, threads about gas mileage are all over. I've searched and read them all (for the most part). But one thing I hadn't seen was a reference to the noticeable decrease with the AC on. My 07 has about 23k miles, finishing up a bottle of STP complete fuel cleaner in it now, thought that was it.

To give you an idea what's going on, a highway trip this weekend, I reset the MPG meter while I was already cruzing at 75. I got about 23.5 mpg's over 40 miles. I didn't think about the AC until today, so I was playing with it around town, and all the numbers I've had in town are up considerably. I had averages around 16 and 17, and I'm now seeing my mileage going up over 20, almost 21 with all the same driving. This includes some hotfooting and a lot of waiting at lights, as usual.

I've noticed at cold starts there's some squeaky sounds like pulleys/belts, but it goes away after a few minutes of warmup. It also comes and goes if I cycle off and on the AC while it's still warming up.

I'm under warrantee, so I'll get this checked out. But I was very curious if a sluggish compressor could actually rob the car of MPGs without me noticing any "seat of the pants" power loss. Car also keeps really cold inside, no noticeable issue there.

I still need to try this on the highway, see if my numbers go way up, but I've read where people are getting 28 and 30 at speeds over 75, so I'm anticipating something bigger.

Any insight welcome.

 

every car will loose gas mileage when running the a/c. it engages the clutch in the compressor which puts an additional load on the engine.

 

√

 

Just to give you a idea, instead of making fun of you Id like to explain that the compressor runs off the engine. It takes alot of effort to run the compressor so your gas mileage will suffer.

 

lol

 

These cars are not made in the early 90's. Compressors are way better built and way more efficient. You will see little loss with your ac on. If you are seeing any at all. Having the A/C on will not be as bad as rolling down your windows if you want a comparison. wind drag has more of an effect than the A/C. If you are going at slow speeds meaning under 50mph then windows down will probably be better than with them up and A/C on. However above that windows up and A/C on would probably be better. This should be tested out by someone and see what the conclusion is. I would but I drive stop and go just about everywhere, and my A/C hasn't worked since I bought the car in 04. I know reading my post was probably pointless but hey the thread is pointless without supporting data for us to evaluate right?

 

today's a/c compressor isnt much different than one of the recent past. it still takes a decent amount of effort from the motor to run it, you will always have a noticable decrease in fuel economy. im sorry but i have to argue your theory that a/c on is cheaper than driving with your windows down.

 

I guess maybe I am being misunderstood. I meant at 75 mph on the highway with the A/C on would be cheaper than having the windows down. I honestly don't think A/C makes a whole lot of a difference. I don't have it and still get 13-18 city just like everyone else. 28 highway most of the time but I have windows up on highway. I have no supporting evidence to prove A/C compressors are more efficient in 2009 vice 1999. I do have a 1996 pathfinder and when I turn on the A/C my engine feels it. This is not the case with my 04 Maxima. Like I said before my A/C hasn't worked since I bought it. I do know the compressor kicks on though because I hear it.

 

Do the people who are getting the 25-30mpg highway have the CVT or the manual trans? I've got the CVT and I've only gotten 13-16mpg in the city, and low 20's on the highway. That's with driving the car easy.

 

i have the cvt and i get 21-22 city consistantly and hwy is 28+

 

I'm no noob, so hold the making fun comments. I'm aware that some drain can be seen with the AC on, but to the extent that I'm seeing 23.5 mpg on a 40 mile perfectly flat trek, when I reset the mpg meter after I'd already reached 75, tells me there's a gross inefficiency in this car currently.

I have yet to get highway time to test the recent theory about the AC, but there are plenty here that are getting 28-30 mpgs on the highway, I'm willing to bet with the AC on. If that's the case, it confirms my theory that something's a-miss with my compressor.

So, those of you with constant AC use, have you noticed low mileage, or are you keeping close to the manufacture's specs...

 

Do you use AC when you're getting 28+ on the highway?

 

75 mph is not the optimal speed, you are using too much power to overcome air drag.
Try 65 instead, you'll see completely different numbers.
Some years back I got a ticket going 81 in 65, so I decided to go slower and I saw about 30 mpg without A/C.

 

Very ****in' helpfull KC

 

I got 30 MPG with AC going 72 for 350+ miles the other day.

I believe there was a mythbuster or something about the A/C debate.

Just checked, and yes there is...



http://mythbustersresults.com/episode22



Followed up by...



REVISITED: Running a car with air conditioning on is more fuel efficient than running with the windows down. (From Episode 22)
partly confirmed
The fundamental flaw in the MythBusters’ test was that the point where the drag becomes powerful enough to inhibit a car’s performance with windows down was inside their 45 - 55mph margin at 50mph. Going less than 50mph it is more efficient to leave your windows down, but going greater than 50mph it is more efficient to use your A/C.


MY THOUGHTS are that there is something wrong with his system... not too sure what though

 

Thanks for the input so far. Anyone out there with a 6.5 gen with the CVT can attest to this 28mpg with AC on at 70mph or so?

I'm pretty sure this is where the problem is. I'll end up at the dealership this week or next it looks like, I still need a straigh run on the highway without AC to 100% confirm on my end. I just didn't want to walk in there with the wrong expectations out of the car, only to find that they will want to charge me for something not under warrantee in an effort to chase down this issue.

One of the selling points for me about the car was that I should have gotten better mileage then my Olds Intrigue, which got decent mileage, but not as good as the Maxima is supposed to be getting...

 

It took "alot of effort" to type that lol.