In the first week of September I made a 750 mile round trip from Boston to Pennsylvania in my 2017 Prius Prime. Some relevant data: The entire trip was made in the Eco mode - only on gas I had one adult passenger and luggage with me. I did not attempt to optimize the drive for mileage or anything like that. The route did involve some hilly terrain, but was mostly flat. I made one stop in each direction, and got a mix of traffic - some stop-and-go, but mostly I was able to drive at or above the speed limit. Mostly above...... I was able to get almost 63 MPG for the entire trip. JT P.S. I also carried a full size spare tire behind the driver's seat, because I was paranoid about getting a flat in the middle of nowhere.
When I drive any distance past the EV range I charge the battery instead of driving in HV. This is highway of course. Using charging mode while city driving is horrendous for MPG. My MPG is pretty good when I maintain the speed limit however sometimes...ok most times I'm a lead foot avg. 75-90. Depending on how far I'm going my avg drops from 102 to high/mid 90's. Nexus 6P ?
The only thing the "Eco" mode does, is change the sensitivity and feel of the gas pedal. It does not change the engine performance or gas mileage whatsoever. (It also restricts the AC a bit.) This has been discussed adnauseum here.
When you are trying to be light on the accelerator by watching the bar graph, you think you are light on the pedal only to look down at the bar graph and see your foot has suddenly become heavier. Having the car in ECO mode lessens the impact. Having it in NORMAL/POWER mode would use more fuel. You accelerate just as fast in any mode when you mash the pedal but a light touch in ECO does affect engine performance compared to a light touch in other modes. Posted via the PriusChat mobile app.
Which is what @Starship16 said. These different driving modes in cars mostly change the accelerator mapping(some change the steering) some that it takes more or less foot pressure to get a certain amount of power from the engine. Eco can help people get better fuel economy through this change in mapping. But it won't help those that can maintain a light touch on the pedal in normal or power mode.
I played around with all 3 modes, several months each time. And I always come back to the PWR mode. I prefer the light, brisk pedal feel. My gas mileage has never suffered. In fact, the mpg is always slightly better when in PWR. It just all depends on how we drive. I routinely get 55-57 (calculated) around town in my non-Prime. That is more than adequate.
I keep mine in ECO, drive 106 miles per day, and have gotten 77 mpg across the first 18K miles at 52% EV ratio. Posted via the PriusChat mobile app.
On long trips I use charge mode when on the highway. ICE is used when stopping for rest breaks, refueling, and getting back on the highway up to speed, and any slow construction areas and bumper to bumper slow traffic. My thinking is to use ICE when it's advantageous and when I need the extra performance (merging onto the highway). My experience is that it seems to help MPG, not a LOT but some. Any drop in mileage while charging is made up when you use the charge. For me it's mostly about having ICE available for those times when it makes sense.
