Open invitation and question to those struggling with their mileage.

[salsaguy]

i agree having a 68 degree set point you are asking for trouble. it will constantly run and never shut off since outside temp is so high. I've read somewhere that most AC units can only efficiently go 20 degrees below the outside temp temp so if outside is 93 at best it can do is 73 so it will struggle to get any lower. the smaller cabin in a car helps (compared to a large house with called ceilings) which is why you should use recirculate mode every so often to reduce load on theA/C unit and boost more mpg.

 

72 or 73 degrees is good enough to stay comfortable. no need for 68

Edited June 4, 2013 by salsaguy

[Recumpence]

The higher the AC set point, the better. I have been running mine at 81 degrees believe it or not. Here in northern Illinois, the temp is not hte issue, it is the humidity. So, I run recirc at 81 degrees. That takes the edge off and keeps me from sweating. However, even that takes 2 or 3mpg off my mileage.

 

I am beginning to think there are differences in various cars, though.

 

Matt

[ScubaDadMiami]

Whatever may come, other than when I travel up north, I will always have the A/C on.  So, you'll be able to hear about any long term effects from me.

[BWP]

Just did a 2,200 mile trip from Arkansas to coastal North Carolina.  3 people, full of luggage, 38.5 trip average.  When in NC, I was getting 45-52 mpg driving around the local area with nice flat road conditions and warm temps.

 

Here's how the wife drove as we crept along in stop and go traffic on I-40 in the Smokey Mountains.   ICE, brake, ICE, brake, ICE, brake, ICE, brake.  And on and on.  

 

Glad I had a good book.

[salsaguy]

I wonder how many marriages will end because of the CMax where the techy husband (or wife) is always complaining to their spouse about messing up their lifetime fuel mpg average! :)

[salsaguy]

Here's an article to help those in the winter with lower mpg's:

http://www.cleanmpg.com/forums/showthread.php?t=17560

 

Glad I live in Sunny So. Cal. and dont have to deal with this

[HannahWCU]

My insights into AC use:

 

When I first cut the AC on the kwh gauge will go real high, but as the car cools, the kwh will drop to below what "other" is showing. I don't use Max AC, but I do use "auto" and start at a temp of 75. Once the interior reaches 75, if the interior isn't cool enough, I drop the temperature in one degree increments until I am comfortable.

 

This doesn't seem to use a ton of battery this way.

Edited June 3, 2013 by HannahWCU

[plus 3 golfer]

I have been monitoring AC usage for some time. Today it was 109*F (highest temp my C-Max has seen) and clear when we returned home. The car was in the sun for about 4 hours. AC set point temperature = 74 F and auto.

When the car is started, climate use jumped to almost 5 kW for about 1 mile - 2-3 minutes where we got on the freeway with eco-cruise set at 67 mph (GPS). Use fell to about 4 kW after about 1+ mile, gradually fell to about 2 kW after another 1+ miles, and to 1 kW after another 11/2 miles. It ran between about 0.5 - 0.75 kW for the next 30 miles. The speed for the last 5 miles was about 50 mph. Total miles = 35.4. FE = 39.8 mpg. Elevation change was + 575 feet. From previous same trips with no AC, I would see about 43 mpg. So that's a drop of about 7% in FE. Once the cabin was cool the climate usage wasn't that bad - maybe 3/4 HP.My guess is the C-Max uses less than 20 HP at 67 mph. So, the FE hit is maybe 4% at 67 mph cruising once the cabin is cool. So, for long term trips in triple digit AZ temps the FE hit will likely approach 4% which is really not that bad.

Since the FE hit of AC will depend on the length of the trip, ambient, and speed, it will be difficult to compare ones AC FE hit with others. Short, slow speed trips with AC use will kill FE as the start-up climate use will be a greater portion of the total climate use over the short trip, slower speed means less air through the condenser and less heat removed or the electric fan has to run to increase air flow through the condenser, and this somewhat "fixed climate use" will be a greater % of the engine requirements at slower speeds . I can see a 15% hit for higher ambient temps, slow speeds, and trips say under 10 miles.

I have also recorded the climate usage for lower ambient temperatures. When the ambient is in the mid 80's the start-up use is reduced considerably (max of about 2 1/2 kW) and the running use is between about 0.3 - 0.4 kW and reached within a couple miles. For our normal 10 - 15 mile one way trips, the FE hit was between 1 - 2 mpg. Bad news is I've probably seen the end of running the C-Max in the mid 80's until October.

One other point and that is the humidity and dew point is rather low in AZ compared to most other parts of the country. So, those in more humid areas will use more kW to remove the water vapor in the air (more latent heat of condensation to be removed) than in AZ. So, the electric compressor will run harder in humid climates than dry climates all else being the same.

Edited June 3, 2013 by Plus 3 Golfer