OK, clearly I'm overthinking things here

I have a 22 mile one way commute to work every morning. I've had my Prius for a bit more than 3 months now, so I've been getting pretty good at maximizing fuel economy on the commute. Depending on traffic and traffic lights and such the car usually displays economy in the high 60's or even in the low 70's on good days. Yesterday I really concentrated on the drive and got my personal best of 75.9MPG on the way in (displayed, not calculated).

Just for fun, this morning I decided to see exactly how much of an impact all this concentration was making, so I turned off the HSI display and just drove the car. I still tried to anticipate lights and didn't accelerate like a mad man or anything, but normally I watch the HSI while I accelerate and try to keep it just shy of the PWR range. Since I couldn't see the HSI on the drive in this morning, I suspect I accelerated a bit faster than I normally do. I also found that I was driving a bit faster than normal. I normally try to keep it at the speed limit, but since I wasn't paying as much attention to it this morning, I noticed that I had drifted up 4 or 5 MPH above the speed limit a few times. Normally the average speed of my drive is 29MPH, but when I checked it after I arrived at work it showed and average speed of 30MPH.

After I arrived at work I turned the display on again to see my economy for the trip. I wasn't expecting too much and I would have been happy if it was over 60MPG... but to my shock it was showing 75.8MPG... only .1 less than my personal best.

I've always been operating under the theory that you need to actively manage when the car uses the electric motor and when it uses the gas engine to maximize fuel economy, but now I'm beginning to think that toyota got it right and that the computer does a pretty good job of managing it on it's own.

I'm also thinking that the slightly brisker acceleration helped my economy (it certanly didn't hurt it, at least) and I may finally break down and get a scangauge. There are a decent number of lights on my commute and a few stop signs. Despite my best efforts with the lights I usually wind up stopping a few times on my trip. If I can use the scangauge to improve my economy during accelation then maybe I can get it into the 70's every day.

 

Haha, that's my problem too... I kept looking down to check as I was driving and it killed me to have it off. I definitely couldn't leave it off all the time.

That's why I'm looking at the scangauge... hopefully I can figure out what I'm doing when I'm not paying attention and do it better when I actually am watching it.

 

LOL... no, it's pretty flat actually (I'm in FL... everything here is pretty flat). I've found that I usually get slightly better numbers on the way to work, vs the way home, but it's only a difference of 2 or 3%.

However, I don't know what it is about the route I take, but somehow it seems to be ideal conditions for good fuel economy. Despite the high numbers I get on my commute, my average per tank economy is around 61-65MPG displayed (57-61MPG calculated) and I can rarely break 70MPG on any other drives.

 

Yes, I think that's definitely the case. I doubt that if I had tried this the first week I had the Prius I would have gotten those numbers, nor am I suggesting that anyone just getting into my car and driving the same route would likely see them. I've certainly learned a lot about driving more economically in the past few months and I still tried to employ that as much as possible.

However, without seeing the HSI display I couldn't really see if the ICE was about to start up and and change my pedal position slightly to stay in all electric mode, or if the ICE was about to turn off so I could adjust my pedal position slightly to keep it on. Frankly, I even tried to keep my eyes off of the instantaneous MPG display so I didn't even always know if the ICE was on or not. This experiment was more a matter of just trying to drive as economically as possible while letting the car make all the decisions about when to start the ICE and when to stay in all electric mode. With the HSI on I tend to try to micro manage that.

Yeah, once my scangauge comes in hopefully I'll finally be able to determine just how fast one should accelerate.

 

I think a lot of it has to do with my commute... as I said earlier I go 44 miles a day, and at around 70MPG that certainly helps keep the average up. If I have to use the car for short trips around town in the evenings or on the weekends then it will definitely lower my average for that tank.

Staying off the highway has been a big boost for me too. The route I'm currently taking to work is all surface streets, but originally I was doing about 15 miles on the highway and 10 on surface streets and I was lucky to get to 60MPG on that route. Luckily my current route on the surface streets is a couple of miles shorter than it would be to take the highway, so I don't lose too much time either.

 

haha... I'd love that too, but I do not know how likely it is... I don't think I've ever hit 80 at any point on a trip... but hey... with a scangauge coming next week there might be hope for me yet