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Most fuel efficient A/C use?

7192 Views 24 Replies 14 Participants Last post by  snowwy66
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?
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Max A/C setting + coolest temperature setting + lowest fan speed = most efficient use.

It it was using to achieve my hypercruzer badge.
 

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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.
 

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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.
 

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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.
 
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