I had my es300h since 2014 and have only used the Eco mode handful of times. I average 35 MPG in regular mode. And when I drove in eco-mode the car easily got 41 mpg on a full tank of gas. So I only used it to experiment, otherwise I always drive in normal.
I drive the RCF once in a while in ECO mode mainly when there is a long stretch of road and just cruising. I average around 14 km/100 liter, which translates to about 17 mpg with 90% in sport+ and manual. 10% of the time in ECO mode. Probably, if I went 50/50 on ECO and sport+/manual, I can get it up to 19 mpg.
We use eco mode exclusively on our CT as economy was one of the reasons for purchase and eco mode seems to give gas mileage for little performance loss (“performance” being wishful thinking in a CT anyway). However, I have never tried it on our GS for any period of time because it seems like a waste to hobble it.
Seems a bit low, even if you are taking off aggressively. Hard to believe that the 6 speed is cutting into your MPG so hard. I would think you would be upwards of 24-25. Oh well...can't put a price on having a great time behind the wheel. Enjoy the ride!
My 17 NX I've driven exclusively in ECO mode. With the heat in South Florida, the reduced a/c is hardly noticed as the NX air is more than adequate. I've averaged just under 25 mpg since I bought it. I don't accelerate too quickly, but on the highway I'll cruise between 75 and 85. I'm more than impressed with that number.