There are a lot of posts on the ECO button, so I figured I'd ask...if one drives with AC on, how much of a difference in MPG will the ECO button yield?
Is it a big deal, or not worth getting upset about?
Thanks!

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Well, I can tell you that in AZ, where it is frequently over 100 degrees in summer...basically May-Sept, the ECO mode definately doesn't cool the car off as well. We took a 100 mile trip on the freeway last week, with outside temps at 100, and with ECO mode, it wasn't comfortable in the car. I switch it on and off occasionally to maintain a comfortable temp.

It is my understanding from an earlier thread that the ECO mode will not cool the car below 77 degress, regardless of the set temp...(which causes the fan speed to constantly incease...on auto setting...to try to keep up). With 100 temp outside and a huge heat load from the bright sun in the desert, the ECO mode is barely tolerable for us. Once the temps get back to the low 90s, ECO seems to work fine, or if it is cloudy, or at night (yes it can still be near 100 with the sun down)

Certainly depends on where you live! Looks like you need ECO-off in AZ, but don't in ME or here in OR.

If you are in milder climes, ECO will cool the car below 77 degrees. The AC compressor has several power ranges and it won't run at full power below 77 if ECO is on. It's a rare day here that it won't maintain any reasonable temperature. We have it set to 73 or 74, any lower and it gets chilly.

I'm more interested in the effect on the car's FE (...reduces by "x" MPG, etc.)...does anyone know?

Other great tools:

• Toyota Online's iGuide
• 2007 Online Owner's Manual
• 2008 Owner's Manual PDF (download link)

Haroldo...Sorry for the tangent.

Also sorry...My trips are too inconsistent to provide any significant feedback for you. I use it when I can on general principles. If the A/C compressor isn't working as hard, it must be saving energy.

Hopefully, someome with a regular commute will be able to chime in?

I try to avoid having it off. When I'm stopped at a light and the engine doesn't shut off, the first thing I check is the ECO button. Turning on ECO allows the engine to shut off. The reduced power air conditioning as well as not allowing the use of the electric heating elements in ECO mode should increase economy much like a two-stage furnace/air conditioner in a home.

At least for us, we are comfortable with ECO on, so the amount of savings doesn't matter -- we are thankful for any we get.

The rate the electric compressor draws energy from the battery makes a difference in things like how soon/how often/how long you can go into EV mode and how much the ICE runs in general to keep the charge up. There is a thread on another forum where Dan (who visits here from time to time) gave more details. IIRC - it is anywhere from 1-2 MPG cost to run in full mode as opposed to ECO - again this would depend on your local ambient temperatures and sun conditions.

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This is certainly unsubstantiated since there are many variables we didn't control, such as fuel quality, pavement, head wind, etc, but on a very extensive trip my family took last summer, our 2007 TCH always returned 42 MPG+ over 600 mile (or more) days, even in the Las Vegas heat. We noticed one day we were having trouble clearing 40 MPG and finally noticed the 'ECO' had been off. I'm sure it was cancelled in the morning for defrost and we forgot to turn it back on. We were down about 3 MPG (about 7% or so). I was surprised at the difference.

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BTW: 'ECO' simply cycles the A/C on and off to approximate the set temperature. If it is off, the A/C will always run and be mixed with heat to more accurately hit your set temp. This is why 'ECO' shuts off when you run the A/C.

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