Fuel Economy and Auto temp control

[pat_smith1969]

A while back there was a post about the Auto temp control and how it always has the AC light on. Several posters thought it wouldn't make much difference in MPG. Well I have done some research/experimenting on my car and over 10 fill ups (defined as adding gas that equals more than 11.2 gallons) here are my averages.

With Auto on (during winter) thermostat set to 69~70 outside temps 20 to 40 F I averaged 235 miles on 11.2 to 11.6 gallons ( about 21 to 22 MPG).

WIth Auto off and the vent blowing slowly (still winter but a bit warmer)
I averaged 285 miles on 11.6 to 11.8 gallons ( about 24 to 25 MPG)

Not exactly scientific but that is a HUGE difference.

 

[GoFast]

2-3mpgs

 

[F430TECH]

Yeah 2-4 actually compare the biggest difference and the smallest difference....

But an average of fifty miles more per tank...thats pretty big...

 

[Maxx Mazda]

It's no secret that A/C is a bastard for gas mileage. Alot of factory "auto" systems leave the A/C on to condition the air even if it's cold out. Like how defrost always uses A/C to dehumidify the air, then heats it to blow on the windshield.

Personally, I like to control when I need A/C. Sometimes I just want hot air on the windshield, not dry hot air, so I disabled my "auto A/C" on the protege. Alot of us have actually, might be something to look into for the 3 guys.

 

[GoFast]

Personally, I like to control when I need A/C. Sometimes I just want hot air on the windshield, not dry hot air, so I disabled my "auto A/C" on the protege. Alot of us have actually, might be something to look into for the 3 guys.

I just turn it off (uhm)

 

[dan1101]

I went through a tank or two with Auto on, and it didn't make much difference for me. I usually get from 300 to 325 miles on a tank regardless.

Day to day I leave the vents set to floor and mid-level vents, the fan to its lowest setting, and temperature to auto.

 

[pat_smith1969]

For my car (I have the GT) no matter HOW I set the vents, fan, ac, anyother setting... If I set the temp to Auto it changes all the settings to some seemingly random setting... the fan will blast, the ac always goes on, and it may change to any of the many vent positions (it seems to like Defrost though).

I am not sure how you are setting all those settings then using the auto temp setting.

 

[Maxx Mazda]

I just turn it off (uhm)

Easier said than done. Mazdas use the a/c in floor, floor/def, and defrost modes, even if the ac button is not pressed or lit up. You have to takethe hvac unit apart and remove the microswitches that cause this.

 

[dan1101]

Yeah Auto seems to love running the AC compressor and blasting the fan.

 

[robin2660]

Easier said than done. Mazdas use the a/c in floor, floor/def, and defrost modes, even if the ac button is not pressed or lit up. You have to takethe hvac unit apart and remove the microswitches that cause this.

Are you SURE it uses AC in floor mode? I am convinced AC comes on only with defog/defog combo (can hear it come on, you know?).

 

[Maxx Mazda]

I know on the pros it comes on in floor mode (not anymore though!) I thought the 3's as well? Maybe not but ya u can hear it

 

[GoFast]

Are you SURE it uses AC in floor mode? I am convinced AC comes on only with defog/defog combo (can hear it come on, you know?).

even then you can shut it off. The auto light will kick on so you just shut it off and there is still air blowing from the defrost vents but no a/c compressor. I do have a GT though so things may be different on a sport?

 

[Jasnall]

/beginrant
The auto feature works as so.
1. Set the temp knob to the desired temp.(Show on the right side of the radio LCD)
2. Press the auto on button.
The car will now try to bring the inside temperature to what you set it to. If its 80 in your car and you turned your knob down to 69, YES the fan will go full blast and begin to slow down until it thinks its at 69.

I've noticed that if its cold outside and you just start the car and crank the auto temp to heat, the car will keep the fan low and blow out the floor or defrost. Once the engine warms up it changes the vents to face and or feet once it is ready to blow hot air.

But YES i've found the AUTO feture will ALWAYS turn the A/C on. I dunno why, And i find it a little annoying somtimes. But in the summer when its 80-100 outside the AUTO feature works fantastic at keeping the temp at what ever i turn the knob to.

/endrant

 

[Maxx Mazda]

a/c on increases the load on the engine and helps it warm up faster. Also the latent heat released by the condensor can help out too. Even when it's cold out the condensor will get pretty warm.

 

[eg6motion]

Day to day I leave the vents set to floor and mid-level vents, the fan to its lowest setting, and temperature to auto.

how are you setting the temp to auto? Auto controls all aspects, if you change anything it turns it off and you just manually set the temp, fan, and blower....

 

[karl hungus]

concur w/ pat smith on the mpg. little peeved that auto mode isn't smart enough not to turn on the ac during the winter.

 

[BillTheCat]

Interesting finds by the OP. I have never even activated my automatic climate control system. I never liked automatic anything in my car. I'll dim the mirror when I wanna, I'll decide when to turn on the windshield wipers & at what speed, I'll select my own gears, and I'll select my own fan, vent, and temp settings, thank you very much.

Hell, I don't even like the idea that the accelerator pedal isn't directly controlling the throttle, but rather, instructing a computer that gets to make the final decisions. I'm not against technology, mind you. I just don't want computers second guessing me or attempting to predict what I want.

 

[LukeP]

I wonder if someone with dashhawk can post engine load numbers from having the AC on, off, auto climate on/off and various vent positions and settings.

 

[dan1101]

how are you setting the temp to auto? Auto controls all aspects, if you change anything it turns it off and you just manually set the temp, fan, and blower....

Hit the auto button, it handles everything automatically. But you can then manually select the fan speed and/or vent pattern and the temperature remains auto, as far as I can tell. I ran that way all last summer and winter and didn't notice it freezing or boiling me.

 

[dan1101]

Hell, I don't even like the idea that the accelerator pedal isn't directly controlling the throttle, but rather, instructing a computer that gets to make the final decisions. I'm not against technology, mind you. I just don't want computers second guessing me or attempting to predict what I want.

Auto mirror is very nice. I like full rear visibility when no one is behind me, so I don't have to keep flipping the day/night lever. The auto wipers are nice when it's drizzly outside. But leave them on all the time and sometimes they'll squeak across your dry windshield on a sunny day.

The auto headlights are annoying, they come on whenever you turn the key on at night.

Is that true about the accelerator pedal? I thought it was cable-driven? Feels like it.