[GRIMland]

Anyone know what the most fuel efficient way to use the A/C in a first gen Cruze?

I've read blogs saying Max A/C setting (recirculate) is actually more efficient than the regular A/C setting, which was news to me but made sense when explained. Does the Cruze mix hot air from the heater core when the A/C is on and temp control dial is anywhere other than coldest setting? I know different types of cars use different ways to do that, but that way would be the most in-efficient.

When I drive alone I only use A/C when needed, and turn off when accelerating or going up hills. When it starts cooling me off enough I switch it off (press button, keep vent going) then when I warm back up I switch it back on and basically manually cycle it as needed.

Anyone have more fuel efficient ways to operate it from a hypermiler's perspective?

 

[Robby]

Recirculate reduces compressor load because you are cooling already cooled, interior air......but some folks notice the air becoming stale if recirculate is used too long.
Turning the compressor off is counter productive......the power needs of the compressor are rather high at startup and operating pressure remains high till the evaporator is cooled (again).
If the car senses too much throttle to negotiate a hill the compressor turns off (bcm command) until the load is reduced.

Adjust the temp knob for a temperature that works for you......higher temp equals lower compressor draw.

Only the automatic A/C systems blend heated air with A/C to maintain a specified temperature.....this is continually adjusted as you drive.

The base system is manually blending heated air as you adjust the temp knob.

Did I miss anything?

Rob

 

[Tomko]

Max A/C setting + coolest temperature setting + lowest fan speed = most efficient use.

It it was using to achieve my hypercruzer badge.

 

[obermd]

The compressor on the non-auto temp versions runs at full tilt all the time. The blower motor, on the other hand, runs at different speeds and has dramatically different power requirements between 1 and 6 (4 for 2011&2012). Run the blower at the lowest speed that will keep you comfortable.

 

[GRIMland]

Thanks guys that all makes sense, and I usually run the fan on 2nd speed of the 6, since 1 doesn't seem to do much. I once kicked up the speed to 6 on panel (no feet) setting with one or two of the passenger vents closed... sounded like the dashboard was about to blow!

 

[jblackburn]

The compressor on the non-auto temp versions runs at full tilt all the time.

Yes, but it changes displacement according to fan speed and pressures. "Variable displacement". This is good though - you're not running the compressor at full displacement all the time and cutting it in and out with a compressor clutch that wears out down the road.

Also keep in mind that the coldest temp setting is auto recirculate. One notch up = fresh air. The recirculate button itself does nothing when the dial is set to max cold.

I definitely get lower MPG in town running my AC, but that's because the car has to work much harder. I usually turn it off to merge just so I don't have to floor it to cut it off. However, my comfort is a much bigger priority for me than MPG, and I love A/C.

On the highway, I notice little difference in MPG having the A/C on vs windows rolled down.

 

[Tomko]

The system in my Cruze is sufficiently intelligent to know when the evaporator is icing up and it opens the recirc door to allow warmer outside air to thaw the evaporator. Once done it auto closes again.

You can tell when the system does this, because the sound of the fan changes as does the volume of air coming out of the vents.

As well there is a noticeable increase in the drag on the engine when running the fan at the fourth speed, as compared to the first, second and third. I'm guessing that this is not only drawing more demand from the alternator, but is also commanding greater displacement from the compressor.

From a physics perspective you are generating the coolest air, and most dehumidified air, by drawing the air as slow as possible over the evaporator. So again, the slowest fan speed tolerable is the way to go.

 

[jblackburn]

From a physics perspective you are generating the coolest air, and most dehumidifies air, by drawing the air a slow as possible over the evaporator. So again, the slowest fan speed tolerable is the way to go.

I've noticed that the vent temp doesn't seem to change between speeds except when I put it on max fan speed (a little less cold there). Makes sense - it tries to maintain a displacement where it's outputting a constant evaporator temperature. That, and I can hardly drive the car around town with it on max because the little hamster engine bogs so much.

I've never noticed mine switch between recirc and fresh air on its own - I can usually smell the difference in the air.

Funny realization - I have a long, steep hill out of my complex that I usually go down in 2nd gear. I've realized that I can control the amount of engine braking I get down that hill just by ramping up the A/C speed. If I put it on max, I actually have to use the gas going down the hill (normally I'd be riding the brakes to the stop sign at the bottom with A/C off entirely)

 

[Tomko]

I've noticed that the vent temp doesn't seem to change between speeds except when I put it on max fan speed (a little less cold there). Makes sense - it tries to maintain a displacement where it's outputting a constant evaporator temperature. That, and I can hardly drive the car around town with it on max because the little hamster engine bogs so much.

I've never noticed mine switch between recirc and fresh air on its own - I can usually smell the difference in the air.

Funny realization - I have a long, steep hill out of my complex that I usually go down in 2nd gear. I've realized that I can control the amount of engine braking I get down that hill just by ramping up the A/C speed. If I put it on max, I actually have to use the gas going down the hill (normally I'd be riding the brakes to the stop sign at the bottom with A/C off entirely)

I almost never have the fan more than at the 2014 third level and most often at two or even one.

I notice the evaporator freezing over more often at the slower fan speeds and after being on for say 20-30 minutes before the first occurrence.

Freezing would also be related to the relative humidity. So it's possible that I'm more humid than you.

 

[Alex V.]

In city driving acceleration is obviously affected when the A/C is on, and I'm sure it hurts fuel economy some but I don't drive regularly enough in the city to notice it. On the highway there's a little power loss, but I can't discern any difference in gas mileage with A/C on or off. A very narrow temp range (unless it's raining = no windows) I'll toggle the A/C on and off every few minutes, but otherwise I leave it on, temp. knob all the way to cold, and use only the fan to regulate the temperature - I've never needed to sustain more than speed 3. Defroster is a different story - I'll toggle it depending on conditions. Sometimes, if I anticipate needing to make an aggressive maneuver, I'll kick the air off ahead of time so I have all the juice from the get-go, but that's very rare.

 

[spacedout]

In city driving acceleration is obviously affected when the A/C is on, and I'm sure it hurts fuel economy some but I don't drive regularly enough in the city to notice it. On the highway there's a little power loss, but I can't discern any difference in gas mileage with A/C on or off.

I loose 6+ MPG with my cruze and now my Sonic running the AC in mixed driving, it seems to loose more in city stop and go driving than steady speed highway. At 55mph cruise set I've seen the same 6mpg drop as mixed driving, however there is enough unused power/RPM at 70-75MPH that I see no significant loss in MPG. it makes a big difference with this engine if your running under 1800RPM with the AC on vs 2400RPM+.

Another thing I noticed, if I'm using my AC I get better MPG if I also use a lower gear to keep the RPMs above 2000RPM, seems the ECU wants to run 1500RPM with the AC on around town making the car a dog and putting the engine under much more load in even normal driving conditions.

 

[salehoor]

at hot country , and at summer time
we always keep it on
put we didn't notice that much of difference between summer and winter

 

[Alex V.]

Another thing I noticed, if I'm using my AC I get better MPG if I also use a lower gear to keep the RPMs above 2000RPM, seems the ECU wants to run 1500RPM with the AC on around town making the car a dog and putting the engine under much more load in even normal driving conditions.

I've never tried that but it makes sense. It's very possible that's the case and I've just never had the car in those conditions for a long enough period to notice. Though mine's a manual and I don't make a habit of putting it under much load at all below 2,200.

 

[Jcote]

Sense on the lines of A/C I find no need to creat a new post.. I have noticed my A/C is running quite frequently when I have my controls set to defrost. I know this is normal but would it be recommended to unplug the compressor during colder weather we’re A/C is not actually required. To help offset some of the weather fuel mileage drops? No matter if controls are set to the hottest setting or not on defrost it cycles.

 

[Eddy Cruze]

Sense on the lines of A/C I find no need to creat a new post.. I have noticed my A/C is running quite frequently when I have my controls set to defrost. I know this is normal but would it be recommended to unplug the compressor during colder weather we’re A/C is not actually required. To help offset some of the weather fuel mileage drops? No matter if controls are set to the hottest setting or not on defrost it cycles.

If something is operating as normal I can't see how it would be "recommended" to unplug

 

[Jcote]

Maybe not recommended but would it be bennificial for fuel mileage improvement during colder months? Truthfully vehicles defrosted windshields for years without A/C

only think i woildnt like about the unplug would be no use would allow the seal in compressor to dry up and fail. So if unplugged all winter long you may end up replacing compressor in the spring.

 

[snowwy66]

Maybe not recommended but would it be bennificial for fuel mileage improvement during colder months? Truthfully vehicles defrosted windshields for years without A/C

only think i woildnt like about the unplug would be no use would allow the seal in compressor to dry up and fail. So if unplugged all winter long you may end up replacing compressor in the spring.

And you just answered your own question on that second line. And it's not just the compressor with seals. Everything ac related in your car has a connection that involves seals.
The compressor is tied in to the defrost so that it gets occasional use to keep everything lubricated and functioning come next year. Otherwise, think of the massive increase in ac repairs.

Supposedly it also helps to dry out the moisture on defrost. Those of us on the west, only have moisture when it's raining or snowing. Or frost. Or whatever. As compared to the east coast where it's almost always humid.
Us westerners really wouldn't notice the moisture dillemma the easterners have.

 

[17Hatch6MT]

vehicles defrosted windshields for years without A/C

I remember having to use rags to wipe fog off the inside of the windshield. Only after the car warmed up did the heat defrost work. And then you had uncomfortably hot air blowing on you, at least until the windshield heated up enough so you could turn the fan down.

I do think the heater-defrosters of the past were better than today's units, that don't have to be as efficient because the a/c dehumidification works so well. Maybe the problem with today's units (in heat only mode) is the a/c evaporator holds moisture that has to be 'burned off' before the windshield starts to defog.

That said, I would like the option to use hot air only & not run the compressor. Too bad we don't have that option any more, without doing 'silly' things like you're suggesting. My old Sentra had an unlabeled detent on the rotary knob that would defrost w/o AC. Unlabeled so it didn't confuse the 90% of people who are clueless I guess.

 

[dougunder]

For what it's worth we just left A/C time here in MA.
I religiously chart millage, more to head off problems then hyper-milling

I didn't see any difference at all this fill up vs previous. 36 and change like always.
Possible it the winter blend tho.

As an aside the MPG the car says it gets is always off vs my calculation. Anyone else see the same?

 

[Tomko]

My first car, a 1984 model year, ran the A/C whenever the defroster was engaged. So it’s not a new function to me - or GM.