Sudden decrease in fuel economy

[F8L]

FWIW, we see similar effects in the Prius. AC current draw can be as high as 1,800 watts at startup when temps are much higher than your climate setting (100F ambient vs. 76F setting).

 

Monitoring via Scanguage and Torque app has shown a 7-10mpg instant drop in FE when the AC is turned on and the load is high. This drop is sustained until the cabin finally cools down and the compressor winds down. This can take 10min or more in really hot temps.

 

Now imagine making many short trips where the AC is working 100% during each trip because you don't drive long enough to cool the cabin down. That is a true mileage killer. :(

[Laurel]

FWIW, we see similar effects in the Prius. AC current draw can be as high as 1,800 watts at startup when temps are much higher than your climate setting (100F ambient vs. 76F setting).

 

Monitoring via Scanguage and Torque app has shown a 7-10mpg instant drop in FE when the AC is turned on and the load is high. This drop is sustained until the cabin finally cools down and the compressor winds down. This can take 10min or more in really hot temps.

 

Now imagine making many short trips where the AC is working 100% during each trip because you don't drive long enough to cool the cabin down. That is a true mileage killer. :(

Yesterday we did several short trips as you describe--AC likely was working 100% each time as the trips were short and the car never got cooled down.  Very interesting info  Thanks.

[salsaguy]

This is when its good to use that "all windows auto down" trick with the fob so you can let some of that hot air out when you get in, then drive a bit with them down, then close them up and use MAX AC to recirculate the warm air till it gets close to your comfort temp (usually 72 or 73 degrees) and then use Auto AC as norm. lower the fan speed so it doesn't use as much of a load. Shut it off it you don't need it.

Going below 72 deg will really put a load on your AC and make your mpg´s suck big time.  you don't need to be THAT frosty!

Edited June 4, 2013 by salsaguy

[Ryan McEachern]

Laurel,

 

I have found that having all the windows down approx 3/4 of an inch works well for me, So far I only use AC when the kids are in the car (DaaaAAAAAaaad, I'm tooooooo HOT!)

 

Our garage stays pretty cool so the car usually starts out at a pretty comfortable temperature, I did seek out the shady parking spots while in town this weekend though.

 

Good luck on your upcoming freeway trip, I have been pleasantly surprised at how good the highway fuel economy is with the C-max, especially after hearing all the horror stories from down south, but I guess our speed limits are so much lower up here that it makes a difference.

[asb]

I was afraid something was wrong with the battery.  Once you go so many miles with the car, you receive the ability to set up a "My View" screen.  I think there are additional options once you have My View.  I switched over to the view that lets me view what the battery is powering and was stunned to see how much the AC was costing me.  I live in Florida where we run the AC most of the time.  I used to set the temperature around 63 to 65 F.  Now I run it around 73 to 75 F and my good mileage returned.

 

Next, I'm going to work on cycling the air on and off.  I have a long commute to work each day, so I have time to play with the car and mileage.

[F8L]

Yesterday we did several short trips as you describe--AC likely was working 100% each time as the trips were short and the car never got cooled down.  Very interesting info  Thanks.

No problem. :)

 

For low speed driving I just roll the windows down. For higher speed driving I use the flow through technique where you crack your driver side window about 4" or so and crack the rear passenger side window about 2-3".

 

Keep in mind that if you are uncomfortable then your battery probably is too. In those cases it is better to just run the AC and promote longer battery life as well as your own. ;)

[ScubaDadMiami]

I live in Florida where we run the AC most of the time.

I consider myself an air conditioner-aholic.  I leave my condo at 68F.  I can't think of a time that I didn't have a car with the AC set on the lowest temp it will go, except for a few days during those occasional winter cold fronts that actually cool things down.

 

I am able to tolerate about 72 to 73 at work.  So, I hope that I am going to be able to find some kind of balance that I can deal with.  :sad: I was reluctant to tint the windows, but I am now absolutely going with it. 

Edited May 7, 2013 by ScubaDadMiami

[asb]

I consider myself an air conditioner-aholic.  I leave my condo at 68F.  I can't think of a time that I didn't have a car with the AC set on the lowest temp it will go, except for a few days during those occasional winter cold fronts that actually cool things down.

 

I am able to tolerate about 72 to 73 at work.  So, I hope that I am going to be able to find some kind of balance that I can deal with.  :sad: I was reluctant to tint the windows, but I am now absolutely going with it. 

 

I hear you!  Not to do the TMI thing, but being menopausal has made it impossible for me to tolerate the heat.  This afternoon I cycled the air on and off and it did pretty well.  But we're having amazing weather right now, so there's no telling what I'll be able to tolerate during July and August.

[Laurel]

Thanks everyone for the AC tips.  Things have improved drastically by using your advice.  We went on a wee road trip to Barnston Island (a farming community in the middle of the Fraser River).  You travel there on an old rusty ferry--sort of a tug boat pushing a barge with a ramp where you have to back off the ferry on the island and back onto the ferry from the island.  Pretty cool little spot to visit on a hot afternoon.  We used the tip to roll down the windows with our fob before getting into the car, not using AC until the car was cool and on the road, and then not setting it to our usual 18-20 C.  We kept it at 22C which was pretty comfortable actually.  Like asb, I have my menopausal moments and had to lower it a couple of times.  But we had a steady 5.2 L trip versus the awful over 10 L trips that we had the other day.  I keep learning so much on this forum.  It's great to learn things so that one doesn't get discouraged and decide to drive your C-Max off the ferry into the drink LOL.  Although hubby said he had a few butterflies backing off and onto the ferry--didn't trust the camera and craned his neck.  Years ago a friend of ours did back her car into the Fraser River on that ferry and she has never lived it down.

[asb]

I'm sure I would be one of the ones to back my car into the river.  I'm glad your mileage has improved.  :)