Unexpectedly, I got 62.5mpg on the way to work, and 66.0mpg on the way home. I'm impressed, especially for a 45°F day, and driving home with the headlights on. These are numbers that would be only slightly disappointing on an Insight, and there are a few important ecomods left to do on the Prius C.
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Perhaps some Prius veterans can chime in here, but this is what I've figured out about the Eco Meter. The Eco Meter is a bit like a tachometer, in that it indicates how hard various parts of the powertrain are working, and how much power the driver has requested.
The blue region is regenerative braking. Braking is bad, for obvious reasons.
The first half of the green region is where EV mode is possible. Electricty isn't cheap, so I use it sparingly. If I can extend an engine-off coast in traffic without drawing much power, I'll do it, but the combustion engine should be the primary source of propulsion.
In the first half of the green region with the engine on, the engine isn't heavily loaded enough to be efficient. This is the vertical part of the BSFC curve at 1000RPM. Stay out of this region.
The second half of the green region is where the engine operates efficiently. This is where I keep it during cruise and acceleration.
The last segment is colored red and labeled "PWR". I'm not sure exactly what happens here, but it sounds like trouble.
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Biggest peeve: once the car is warm, it will let you accelerate up to 45mph or so without turning on the engine. It has a 1KWh battery, which should be good for at least a mile or two. But I have to resort to trickery to even back out of my driveway without it turning on the engine. That's especially sad because the combustion engine is only a hindrance to rearward progress.
The car is programed to try to get its catalytic converter hot within a certain number of minutes of being turned on. So instead of waiting until I'm on the main road to fire up the ICE, it does it three seconds after you power up the car. For now, I've exposed the shift interlock override so I can park the car in Neutral and pull it out of the garage by hand. Then I start the car, and I have three seconds to get the car rolling backward before I have to be in Neutral. It won't start the engine until I shift to D. I really want the ICE to stay off until I get out of my neighborhood and out to the main road, where it can warm up quickly.
The long-term solution is to trick the car into allowing me to use EV mode right off the bat. I wonder if a coolant temperature hack would do the trick. It would be amusing to repurpose the presently-useless "EV Mode" button for the task.