Walt,
>
> Thank you for the reply. The information is very useful.
>
> As one would expect, there's a huge hit in mileage on the highway between
> 55-70 and 80+. I live in the Berkeley hills (across the Bay from San
> Francisco). Every trip I take starts and ends with a very long, steep
> hill -- a cab driver once told me that our street is the steepest street
> in the Bay Area, including all the San Francisco hills. Clearly, coming
> up this hill once or more per day is taking its toll on my gas mileage.
> On the other hand, compared to the car I replaced with the Highlander -- a
> 2000 Ford Explorer -- I am getting great mileage.
>
> I was interested in your comment about the battery. I have not noticed
> the battery bars ever going down more than two. Also, it seems that no
> matter how gently I step on the "gas pedal," once the car reaches 15-20
> MPH, the engine starts. I'd never driven a hybrid before buying this car,
> but I was under the impression that it used the electric motor more than
> mine seems to. I will discuss all of this with the dealer when I take it
> for the first service in 2,500 more miles.
>
> John
>
I used to live in the Bay Area, and those Berkeley hills are steep! I used to love driving through those hills and the hill that goes over the Caldecott Tunnel into Orinda.
The hybrid system provides low speed propulsion and some assistance at higher speeds, and accelerating (as opposed to cruising at a steady speed) uses a lot of power, so the internal combustion engine, or ICE, will start and take over propulsion above 15 or 20 MPH, as you are experiencing. Running under pure electric power rapidly depletes the battery pack, so if you were to cruise at 10 ~ 15 MPH, the ICE would probably start after a mile or two.
The hybrid system reduces the work that the ICE does, but due to limitations in battery storage capacity, the reduction in the need for the ICE to work is probably more in the neighborhood of 5 or 10%, not 25 or 50%.