This has been asked before.... but I can't seem to find the answer...

What ... specifically!!! ... does the ECO button do when it is turned on???? It doesn't seem to make a difference in MPG. But it does make a difference in the ability of the AC to cool the car ... and keep it cool ... on a Texas summer day.

 

My knowledge of the ECO buttom during my test on a cross country drive was that with the ECO button on, the air coming out the vents was 10 degrees warmer. Did this last September on a drive from Kansas City to Denver. With the eco button on, the air would cool to 60 degrees while without ECO the air cooled to 50. Made a big difference on comfort level in the car when driving into a hot sun ... in addition, the fan speed was much higher (trying to cool the car) when the ECO was on. So would have to assume that the AC pump had to run a lot more to cool the air more, so would have an impact on fuel used. I didn't noticed the difference when driving a 75 mph; however, at slower city speeds it may have more of an impact where you get your better MPG.

 

Thanks MileHigh!

I've found the same thing. The HVAC just doesn't cut it over 90F and in bright sunshine. A shame! Our driving is about 50/50 highway and city. In town we can usually do about 35 to 45 and there's few stop lights. ECO "ON" doesn't seem to make a difference in mpg under these conditions.

Where we loose 'charge' and increase fuel use is when sitting at a drive through. Even under those conditions I can't tell a big difference... if any... regardless of the ECO's mode.

I'm thinking it doesn't make any difference on the road above 40 since the ICE runs all the time.

Any idea what the ECO does in temps below 50F? I read somewhere that there's a supplementary electric heater in the HVAC.... then there's supposed to be some type of heating elements in the coolant system to speed warm up. Does the ECO control those??? God, what a mystery!

Thanks again...

 

My guess is that the ECO mode simply cycles the compressor off more than the Non-ECO mode. We used to have a 1988 Camry that had the ECO mode button and if I remember correctly that one did affect the cycling of the compressor.

 

It really would make sense to have the ECO button actually do something "ECO".

But, they haven't gone there, yet. In these cars, it just makes the air conditioner a little lazy. No effect on anything else that I know.

I would like the ECO feature to also have an effect on the cruise control. Maybe give the CC a little more hysteresis, to let it slow down gradually when going uphill, and regain the speed when going down. It wouldn't make much difference on big hills (mountains). But, it could make a useful difference on mostly-flat highways with small hills and bridges over other roads.

 

I like your cruise control idea....!!!! It would really be a plus on the Sienna van. You could tie it in with the VSC (which auto shifts the trans to a lower gear on a down grade if you tap the brakes).

Maybe some black tape for the ECO button, then????

 

Mine has virtual black tape over it.

I turned it off a long time ago and don't even think about it anymore.

 

The ECO button does a number of things. ECO limits the inverter powering the A/C electric compressor to half power (I think the AC uses around 2KW max with ECO and 4KW max without ECO.) ECO disables the 1KW electric vent heater, and allows the ICE to shut off at a lower coolant temperature, saving gas as you come to a stop and wait for a light to change.

If you use the front defroster, or set the cabin air temp to HI or LO, ECO is disabled automatically.

 

Thanks Nash!! This info may help me design a strategy for using/not using the ECO feature. I think a lot of the savings w/ ECO on depends a whole lot on your driving patterns and environment.

 

As I just purchased my TCH, I am not all that familiar with its A/C system. But like most cars of this type, the A/C has a huge impact on FE. I have found in my other hybrids that setting to fan the higher speeds and keeping the temperature setting up a little bit higher than 'normal' allows you to feel very comfortable and helps reduce the amount of time the compressor runs, thereby increasing FE. For example, if you would normally keep the A/C temperature on AUTO to 75, set it to 77 or 78 with the fan at high.