Really embarrassed to mention this, but it happened so easily thought I would mention it here.

Noticed a few weeks ago my gas mileage started to drop from 26 MPG down to 24 MPG and still dropping. Turns out I hit the A/C button on the heat/cold control, who knows how long ago and the compressor had been running everytime I ran the car. Didn't notice the light on till a few days ago now my mileage is almost back up to 26 MPG.

LOL!!!

TomR

 

Well...we all do something silly every once in a while so don't feel bad. At least it's something you were able to rectify and didn't take it into the dealer to have them tell ya that.

 

Be happy...many cars out there, when you turn on the A/C, every time the compressor cycles, it feels like someone just threw an anchor out the window...the car feels like it suddenly had to drive through a massive puddle, just from the extra load the compressor puts on the engine.

If you can drive a car with the AC compressor cycling, and not notice....you're doing fine.

 

now that would of been just really

 

Presumably with the HHR's drive-by-wire arrangement, it's easy for the ECM to make a predictive adjustment to the throttle as the compressor is cycled, making the load change less noticeable, I know that my Dodge did this using the idle control valve, and my Saab had an extra air valve to do this.

 

My other cars also have the IACV feature...but when that big compressor would kick on(for example-using defrost cycles the ac compressor as well), you could feel the load change on the motor.

On my 94 Mark VIII, which averages 24-26 mpg, the AC compressor useage would drop the mileage down a good 3-4 mpg as well.

 

Doesn't the compressor kick on in defrost modes also?