I had my boss with me on a drive the other day and we had the A/C on. Full power. Not in Econ mode. So at each stoplight the car and A/C kept running. How painful to watch the mileage dwindle before my very eyes.

Originally this had been a trip I was looking forward to take by myself. Flat roads. Middle of the day. Light traffic. Warm temps. Nearly mpg nirvana.

But with that darn A/C on, a trip that hould have been in the 80's for mpg was, instead, barely in the 50's!

Fortunately, I've had some excellent trips since then and managed to bring this tank back up to ~73 mpg. But it would be even higher if I could have skipped that trip.

Are there any statistics on how much the a/c affects mileage? If not, I am going to continue to use the unscientific phrase, "a lot!" to quantify its affects.

Eric Powers

MHG Organizer - www.MadisonHybridGroup.com
Hybridfest 2008 - A Hybrid Electric Car Show and More! www.hybridfest.com
Madison, WI July 19 & 20, 2008

Hi Ericbecky:

___With the MDX, it’s about 4 - 5%. With the Corolla, it’s about 7 - 8%. With the 5-speed Insight, it’s as high as 40%! You weren’t seeing things by any stretch of the imagination. Lean burn is shot to hell and the load on the ICE kills it off another 10 - 15% on top of that. I mean most here wouldn’t care given they are probably receiving 55 mpg w/ full A/C but to give up upwards of 40 mpg is almost highway robbery!

___A diesel is the real answer to this problem …

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net

I'm not sure if Insight has climate control.
In HCH case I set the temp dial to about 4:30 position and the compressor cycles short intervals once in a while.
I avoid this if at all possible as the drop is about 7MPG.

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT

Hi Hot_Georgia_2004:

___Yes, the Insight has Auto temp control …

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net

I see at least a 5mpg diffrence with the a/c on my TDI diesel.
This was a recent observation by me on my last tankful.

Theres a very interesting thread on MPG and A/C on another forum, they talk about incresing mpg by using reculated air v.s. outside air, and go on to possible modifications. You might find it an interesting read, and find some usful info.
Improve A/C performance & Fuel Mileage

i just had a sun/moon roof installed in my '05 hch and i love the fact that i can crack the thing to allow for adequate air flow and always keep the air on off, except when its too cold; but this is california so it rarely happens even in the rain. the mileage reduction because of air flow is a compensator of course but it is still better then when im using the fans or fan / compressor combo to cool the vehicle...

but i drive with all 5 windows down, even more so now; but this tank is still well over 50 mpg and it looks like i should be able to top 600+ miles on a at-pzev tank of only 11+ gallons.

I've read a lot of material about A/C in cars, and talked to a number of different dealership service managers. The general consensus is that A/C, in a traditional engine belt driven configuration, hybrid or not, does have an impact on fuel economy. But unlike 25 or more years ago, that impact is less due to more efficient compressor design, lower volume of refrigerant charges, less friction in the A/C compressors and other systematic design improvements. This is just good engineering design and progress. So, if you never turn on your A/C, then the compressor has no opportunity to engage and load down your engine and as such you will ideally run with optimum efficiency.

But the other comment made in print and in person is that if you choose to not use your A/C you will loose it eventually. In an A/C system, refrigerant and oil are circulated throughout the entire system at the same time. The oil lubricates the compressor, but it also keeps rubber seals fresh and prevents them from cracking. If you don't use your A/C the oil doesn't get circulated through the system and as such, over time, seals will tend to shrink, crack and leak. The refrigerant then leaves the system, and your A/C will not work at all. This is a bad situation even though the current refrigerants used do not contain CFCs, it still isn't all that advisable to be letting it out into the atmosphere.

To keep an A/C system running properly and lubricated. The system should be run for at least 10 minutes straight monthly, including winter. Since most cars use the A/C compressor as a dehumidifier in the winter when in defrost mode, that usually provides plenty of compressor use without having to actually turn on the A/C system. The same can be said of most auto climate systems. If they are left in full auto to their own desires at a reasonable cabin temp setting, the a/c compressor will run more than enough to keep the system lubricated.

It isn't worth a couple MPG to let my A/C go down the tubes.

It has been said:
Hybrid drivers come in 3 flavors, greenie, techie and cheapie. Pick any 2.
2005 Prius, Melinium Silver over gray, package 5 (AI)