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How much does A/C affect mileage?

14K views 36 replies 29 participants last post by  rodhower 
#1 ·
How much does the AC affect mileage? I am driving through the desert if all goes well and I end up with my insight in Phoenix. I know I'm going to have to use a/c driving back to cali- any tips on how to keep the mpg high using a/c aside from driving slow?

I am so excited, I just can't wait. If I don't get this car in Phoenix, I'll be crushed, but I'm not going to let the dealership take advantage of me.
 
#3 ·
alson while in econ mode you can select ac or no ac... if you cycle between them it works very well since you only need to put the ac on for a couple seconds to get almost a minute of cold air (depending on temp i guess).

also, try to run the ac going down- especially while coasting as your mpg won't be effected there. don't use it going up hill.
 
#4 ·
in my insight it costs about 10 mpg. i do it the way goat said, with very little impact on mpgs. be aware: a setting higher than 60 degrees seems to just mix in hot air with the a/c air. i dont know if it causes the a/c compressor to cycle any shorter. seems counter productive to me.
 
#6 ·
Excellent tips.

I do strive for mileage, but if it were me driving through the desert, and it was hot as....well, Phoenix. I'd enjoy the AC and smile knowing I'm still smoking anything else out there for mileage. If it isn't too hot around here, that's 50 out of 52 weeks of the year, I just open the passenger side window the tiniest amount dial the AC to cold and make sure it is really OFF by hitting the Econ button the majical 2 times. ;)

Still, if you want to tell your friends how you crossed the continent on one tank of gas when you get back, you can always take along a spray bottle of water, like Uber hypermiler Wayne Gerdes used to do! :roll: :badgrin:

Enjoy the trip!
 
#8 ·
I have a CVT, and I don't think the AC affects it as much as the stick shift(probably because stick shift get's such better gas mileage.)

Running the AC heavily in "Auto" mode probably drops my mileage by 5 MPG. Running it in "Econ" mode only drops the mileage by 2 or 3 MPG. It depends on the temperature though. There are some days when the AC barely runs, and it hardly affects the mileage at all.

James
 
#9 ·
The first time you hit it the AC goes into econ mode which means the compressor and engine shut down when the Insight is stopped. The second time you hit it it actally turns the AC OFF. Otherwise you can have the AC compressor on and be blowing warm air into the car. :shock: This is great for defogging the windows but it really hammers the mileage, (spoken as a hypermiler wannabee). I suspect that many people are blissfully driving around with the AC compressor running and are unaware of it, wondering why they can't achieve lean burn!. I searched for documentation on this and could not find any. After two or three days of frustration, where I was ready to pull the AC fuse, I happened upon this discovery. If any one out there can point me to documentation on this, great. I believe the other way to run the fan without the AC is to push the fan speed button only. Not sure.
 
#10 ·
a few weeks ago i installed a bright blue LED on the dash that is powered from the a/c compressor relay. whenever the compressor is on, the LED is glaring at me from the dash. its a great reminder to turn it off! :D
 
#11 ·
Just checked A/C mileage vs no A/C yesterday. In South Florida, 85 degrees, no wind. 90 mile trip each way---Initial trip segment mileage, windows down, was 79.9 mpg. Return trip segment, windows up, A/C econ mode, set at 72 degrees, mileage 66.8 mpg for a difference of 13.1 mpg. It just shows how efficient the Insight is if the A/C load changes the economy so much.
 
#12 ·
2001 CVT, just shy of 36,000 miles, 56.1 LMPG. My Beloved drives without regard for fuel efficiency, although I do, and I estimate I drive it 80%+ of the time. I normally get 600-650 miles a tank... :eek:

Our a/c has been on the Econ setting, at 72, since we bought the car new, and it has almost never been turned off, not in winter, not in summer. I estimate window-down driving with a/c off at less than 300 miles total. When it's nice enough to drive with windows down, we take the 'vert out... :lol:

We don't sweat the mileage as much as others (not that there's anything wrong with that, as Jerry Seinfeld would say), but My Beloved, bless her Texan heart, would rather stick a pen in her eye than drive without a/c, so even when she's not in the car with me, I'm used to it and don't really think about it. Still, even with comfort as the main issue, we still get better mileage than anything else out there. I say, cooool it through AZ, it's well worth the few extra bucks in mileage hit you'll "suffer." :roll:
 
#13 ·
I would say that running A/C in summer costs me a 10-15% loss in mpg. Losing 10% mpg on a car that gets 60 mpg (6mpg) seems like a lot when compared to the same 10% loss on a car/truck getting 20 mpg (2mpg). I would be curious how the electric A/C in the Prius affects mpg?
 
#14 ·
A/C and mileage

I'm in Phoenix, and it's 105F on May 18th. First, mileage in my CVT Insight has dropped as much as 20%, with the A/C set to 76F. That's where you have to set it in this heat, and forget the Econ mode--it's just too d*** hot. Time to max the tire pressure, and lighten the car , losing everything you can, but keep the spare tire!

Ricco




8)
 
#15 ·
Re: A/C and mileage

rslatin said:
I'm in Phoenix, and it's 105F on May 18th. First, mileage in my CVT Insight has dropped as much as 20%, with the A/C set to 76F. That's where you have to set it in this heat, and forget the Econ mode--it's just too d*** hot. Time to max the tire pressure, and lighten the car , losing everything you can, but keep the spare tire!

Ricco




8)
Ditto, my answer for hyper milers is to crack the windows and run the fan on vent... can't deal with 120+* temps in the cab (after Iraq, its easy for me :badgrin: ) then use a pulse glide AC technique.

I have found that 60, 76degrees whatever, ANY engagement of the A/C compressor severel impacts MPG. The difference for me between 60* and 80* is less then 2 mpg, and so I leave my fan setting to max, and temp to 60. On braking, downhill, or other opportune times that the extra engine load will have minimal impact on my FE, I tap it over to A/C Econ max fan. on ALL accelerations, I ensure the A/C is set to A/C Off and vent on full. In most situations it keeps my cab bearable, if not comfortable, give it a try in a high humidity local and let me know how it fairs there!
 
#16 ·
Should you choose to run the A/C, either Econ or Full-On, be sure to put the vents in "recirculate" mode. This keeps the A/C from pulling in hot, humid (out here anyway) outside air into the cabin and reduces the cooling load.
 
#17 ·
I would say that running A/C in summer costs me a 10-15% loss in mpg. Losing 10% mpg on a car that gets 60 mpg (6mpg) seems like a lot when compared to the same 10% loss on a car/truck getting 20 mpg (2mpg). I would be curious how the electric A/C in the Prius affects mpg?
I doubt a car or truck would lose anywhere near the same percentage as an Insight. Both cars will likely burn near the same amount of fuel in gallons per hour to do the same amount of cooling, but that will work out to being a larger percentage on the Insight than any other vehicle, as its overall mileage is so good.
 
#18 ·
I've found that running A/C makes getting over 80 mpg a nearly impossible and frustrating experience. It's narrows the Lean-burn window far more than cold weather driving, and as such, effects my FE far more than anyone else here, I think.

The few times I've tried to use A/C, my 80 mile round trip commute that I've been getting around 100-103 mpg on droped to the low 80's to upper 70's. The biggest problem is that many hypermiling techniques are simply impossible with the A/C on. For example:

Accellerating in LB is practically impossible. In 5th gear, with A/C on, and compressor is running and my FCD is showing 75mpg instantaneous, I can barely old around 45 mph or so, with almost zero acceleration.

A/C pulse techniques are fairly useless as well. For me, the extra hassle to managing turning the A/C on and off, with the hit in both FE and performance, coupled with the cabin temperature fluctuations make using A/C an exercise in finding new and creative way to curse.

Personally, I'm much happier just simmering with the windows down in 110 degree weather. Once you get used to it, it really isn't all that bad.
Then again, I'm probably a bit more hardcore than most.
 
#20 ·
No one has mentioned a noisy A/C compressor. I think my A/C is louder than it should be, but it's hard to tell for sure, because it has been so gradual.
Also, I can feel the car lose power when it kicks on, and gain power again when it stops.
My mpg has dropped off this summer, but I bought a set of non-LRR tires at the same time, and also I replaced an A/F sensor that was causing DTC codes. Both of these things can change your mpg, so I confounded the issue.

Has anyone noticed an A/C compressor getting noisy, causing poor mpg, and needing to be replaced :?:

- Jim
 
#23 ·
Tuesday I had an errand to run and drove 38 miles getting 83.1 mpg (cvt, not manual trans). I had the hvac off, and the windows down, was real hot but doable. Later in the day I went out with my wife and had to run the ac for her. I only got in the low 60s for mpg. That was nearly a 20 mpg hit just due to the ac.
 
#24 ·
Don't forget the added weight of another passenger makes a difference as well, especially in a G1.

Sorry about mentioning weight in a thread where a wife is mentioned. :)
 
#26 ·
I would tend to agree with you on the weight thing. I have maxed out my FCD 5 or 6 times on drives around home and 2 or 3 of those were with my wife in the car. The most recent was this past Tuesday evening on the way home from DQ when I hit 156.8 mpg over 11 miles.
 
#27 ·
Isn't this somewhat a function of speed? In Florida, it's more or less impossible to survive in the summer with the windows up and no AC. I've read that there is a break point where the aerodynamic hit from having the windows down outweighs the drag from the AC compressor.

Can anyone confirm?

I tend to drive around town with the windows down most of the time, and keep the windows up at speeds above 55 and use the AC as needed.
 
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