The MPG problem... Solved? Read!

[gadgetguy]

UPDATE!!!!UPDATE!!! UPDATE - I did an entire tank of Gas with absolutely zero HVAC - never touched the button once for an entire tank of gas... mind you this was Tampa Florida (for the people saying... texas and wherever else... yes it was fricking Hotttt, but I had to test it).

 

With A/C: total miles obtained based on multiple reciepts: apprx 384 per tank = 38.1mpg

 

With NO HVAC System: total miles obtained based on this reciept: 480.1 for this tank = 48mpg (25% Difference)!!!!

 

THIS IS REDICULOUS!!!! So, apparently we aren't supposed to use the HVAC to get good mileage.

 

I usually use my A/C in the afternoon's when the heat and humidity are high. If it is a mild day I won't. The trips I make w/o I will typically get 48-53 mpg depending on where I am going. In the afternoons with it on I get 40-45 again depending where I'm going. Yes there is a 5 mpg window but as we all know there are so many environmental factors that can effect mpg that it does vary. The A/C does drain the battery pretty quick if on full blast so I try to not let it run that high.

 

Its just as you do with everything and that is you moderate it. No biggie to me.

Edited June 17, 2013 by gadgetguy

[brcd131]

Set the MyView screen to energy usage, and you'll see that once the car interior temperature stabilizes, the energy usage for Climate (A/C) is the same or less than Other (every thing else). The key is to have the A/C on Recirc so you are not cooling the hot outside air.

[FFHTuxedoBlack]

When I picked my car up it's mpg was 25.6, I am now at 39.2 and I run the air about 50% of the time, and my mpg is still climbing. I would think that A/C could take a 20% hit out of the fuel economy. I would like to see what it does if you keep the A/C off for a couple of weeks and see how the mpg's improve

[mcalli27]

I use it and average 45-47 MPG. Of course it's not quite as hot up here, but there are ways to use it without letting it drain all your battery. I never let it run full blast, ever. If it's 90 degrees outside, I set it to 85 and let it cool to there. then I take it down little by little until it's to comfortable levels.

Do you use the "Auto" function or just the fan by itself or use the A/c on lowest fan speed with recirculate... ? It just doesn't seem possible, there is no way I can pull off 45-47 with this thing on... our feels like temps lately have been in the 115 range (in Tampa). So maybe it's just because it's waaayy too hot.

[mcalli27]

When I picked my car up it's mpg was 25.6, I am now at 39.2 and I run the air about 50% of the time, and my mpg is still climbing. I would think that A/C could take a 20% hit out of the fuel economy. I would like to see what it does if you keep the A/C off for a couple of weeks and see how the mpg's improve

This was the whole point of this particular feed... Lol. I did exactly that... read up a few posts. I went from 38.1 (average over a few months) to 48mpg ( based on one entire tank of gas). Never once have I gotten more than 39 on an entire tank of gas until I completely turned the HVAC off for a full tank of gas... 25% difference for me.

[hermans]

Do you use the "Auto" function or just the fan by itself or use the A/c on lowest fan speed with recirculate... ? It just doesn't seem possible, there is no way I can pull off 45-47 with this thing on... our feels like temps lately have been in the 115 range (in Tampa). So maybe it's just because it's waaayy too hot.

That's the way I do it and I get 45+ even at 60-65 MPH.

[mcalli27]

 

I was in FL for a week and used my a/c everyday, it was above 90 the whole week and i even took a drive from orlando to tampa

 

going

 

 

and return trip

 

 

going the posted speed limit both ways

hmmm... perhaps there is something wrong with my car... don't think I would get that good of mpg...

[mcalli27]

That's the way I do it and I get 45+ even at 60-65 MPH.

the fan by itself is not the same thing as the fan on lowest speed with A/C (A/C button can be turned off and it's literally just a spinning fan). So... I'm assuming that your A/C button is lit up then? Is it on the "AUTO" function?

[hybridbear]

On our road trip we've mostly used AC non-stop. There have been a few periods (first thing in morning or late in evening) where it has been cool enough to switch to just vent and I have not been able to see an appreciable difference in MPGs. My guess is that at 65 or 70 MPH and 80-85 degrees and sunny outside the AC only costs us about .5 MPG maximum. This is because once the car is cool the energy required to keep it cool according to the energy consumption graph is roughly equal to the electricity required to run the rear defrost in the winter or the heated seats.

 

In the city on short trips with a hot car the AC penalty will be much higher. This is why aaronj's tip is so valuable to reduce that penalty on short trips

[hermans]

the fan by itself is not the same thing as the fan on lowest speed with A/C (A/C button can be turned off and it's literally just a spinning fan). So... I'm assuming that your A/C button is lit up then? Is it on the "AUTO" function?

I don't use the fan by itself. I use the recirculating AC with the fan on low.

[lolder]

AC load can vary enormously. Try to park in the shade and open all the windows for a few minutes in a heat soaked car before turning on the AC. It will cool down just as fast. Use a sun screen for the top of the dash.

I did some tests a few years ago that showed the AC load was less at 60 mph than at 30. That can be attributed to two things; less radiator fan use and more cooling of the external body by airflow. I agree that the AC mpg hit can be as low as 0.5-1.0 mpg but that's only with highway conditions like hybridbear mentions. I always run the AC in auto when it's on. Low circulating fan speeds don't save much energy.

[aaronj1159]

AC load can vary enormously. Try to park in the shade and open all the windows for a few minutes in a heat soaked car before turning on the AC. It will cool down just as fast. Use a sun screen for the top of the dash.

I did some tests a few years ago that showed the AC load was less at 60 mph than at 30. That can be attributed to two things; less radiator fan use and more cooling of the external body by airflow. I agree that the AC mpg hit can be as low as 0.5-1.0 mpg but that's only with highway conditions like hybridbear mentions. I always run the AC in auto when it's on. Low circulating fan speeds don't save much energy.

This explains why I don't see much variation in AC usage. I only run mine when I'm going to be driving above 55 MPH.

[jeff_h]

I don't use the fan by itself. I use the recirculating AC with the fan on low.

 

That's the same thing I do, if I run the AC then it is set to recirculate and the fan is on the lowest setting and up one notch if needed, maybe up to third notch if it's a hot day over 90, etc ... I never use the 'auto' climate setting.

[Da0ne]

i usually run 'auto' with vents closed at 72 degree

[elle]

I run manually-- "My Temp" is 70 degrees and after things cool off I tweak it up to 72. Do okay this way.

 

In the mornings here, it's cold, but instead of running the heat I just use the seat warmer and turn it off once it's warm. I find that is plenty to take the edge off if the 50 degree mornings and it doesn't seem to impact my mileage very much.

[terryb]

I tried trimming back on the fan this afternoon and I was grinning at the decreased draw and increased instantaneous mileage when the A/C went whacko and flooded the cabin with ambient air (reading 101 at that time) I have not been able to get cooling except with max air since. Anyone got a clue? search so far has been fruitless.

[JonE]

Another Minnesota FFH user reporting in...

Just starting to use the AC occasionally as it heats up into the 80's today. So far, from March when I purchased, my lifetime average is 44MPG. It did get better as the car broke in, or I got broken in (learned to drive the thing). My driving is mostly city with mixed highway and streets. No major freeway trips so far, but will have one down to Madison, WI this weekend. I expect that the MPG will drop. Keeping comfortable definately costs something in mileage as the MPG was poorer when it was still cold here and will take an expected hit as I use AC. I definately think this is the car to have if you do alot of commuting and city driving. Many of my trips can get over 50mpg in town. So far I am impressed. We'll see on the "highway"/freeway...

[lolder]

You might try disconnecting the negative 12 vdc battery terminal for a minute with everything off and reconnecting. Then try the AC in Auto and recirc.

Edited June 20, 2013 by lolder

[terryb]

I took it to the dealer this morning. The only way to get cold air was to run at LO temp setting, which is full blast. My guess is the cabin temp sensor went south so only "I don;t care what temp it is make it colder" works. Raise the temp setting one notch and the compressor is shut down. Whew HOT.

[TX NRG]

I took it to the dealer this morning. The only way to get cold air was to run at LO temp setting, which is full blast. My guess is the cabin temp sensor went south so only "I don;t care what temp it is make it colder" works. Raise the temp setting one notch and the compressor is shut down. Whew HOT.

So did the dealer's diagnosis agree that it is a bad temp sensor (after only 6 months of operation) and did they replace it and fix the problem for you?

[phantomtech]

I tried trimming back on the fan this afternoon and I was grinning at the decreased draw and increased instantaneous mileage when the A/C went whacko and flooded the cabin with ambient air (reading 101 at that time) I have not been able to get cooling except with max air since. Anyone got a clue? search so far has been fruitless.

It might be related to a problem that I had with the Climate getting stuck on hot air. I rebooted MFT using some reboot files on a USB and it fixed the problem.

 

http://www.blueovalforums.com/forums/index.php?/topic/53753-mft-climate-control-stuck-on-hot/&do=findComment&comment=853182

[terryb]

The dealer reloaded my MFT and it was OK today. The mileage is sure as the dickens not solved on my car though.

Edited June 22, 2013 by terryb

[mcalli27]

Hmmm... I see some people are having better success with the AC. It's been High 90's lately here in Tampa. I drive about 30-40 miles per day roundtrip. The mpg problem is simple for me... If I use AC I get crap mpg, if I don't use it I too sometimes was able to get 47-51mpg. This past week (7-10 days) I have been very mildly using the AC function (no "Max") and already my mpg for the week has taken a significant hit down from the 48mpg (for a full tank of no HVAC use) to about 43mpg... have to admit I'm a little disappointed. God forbid I want to stay comfortable without saccrificing 10mpg. I just didn't realize I would have to sacrifice comfort for better mpg. Call me whiney if you want but when you pay $30,000 for something you have a certain amount of expectations to be met. If this was any other product we could return it usually within 30-90 days... doesn't work like that for a car. I'm not saying I would return it if I could but I'm just saying that they kind of have you by the balls (depreciation) and I just wish I wasn't mislead is all (advertising 47mpg, when it seems like 38 is the national average). In retrospect I would have still bought the Fusion... not sure if I would have went with the hybrid though.

[murphy]

Do you have your A/C in recirculate mode?

It takes a lot less energy to keep cabin air cool than it does to cool down superheated air coming in from outside.

[Waldo]

The problem with A/C fuel use is all about the math. Cooling a hybrid requires pretty much the same amount of energy as a regular Fusion, there isn't much you can do to change the physics behind that. The amount of fuel needed to create that energy is pretty much the same on a hybrid as a regular Fusion. The problem is that MPG isn't a measure of fuel use, it's the inverse. So increasing your MPG number doesn't match an increase in fuel use in a linear way. In other words, running your A/C represents a greater percentage of fuel use on a hybrid than it does on a non-hybrid. Thus while you might lose 10mpg on an FFH when running the A/C (dropping from 47 to 37mpg say), the amount of fuel used to run the A/C is the same as if a regular Fusion dropped from 25 to 20mpg.

 

So instead of getting all upset that you're losing such a large MPG "number" when using the A/C, calculate out the actual amount of fuel used and you will find it's not as much as you think.