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Found the Sweet Spot!!

Discussion in 'Gen 2 Prius Fuel Economy' started by Rangerdavid, Apr 24, 2009.

  1. Rangerdavid

    Rangerdavid Senior Member

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    Ok, so today I drove from Boone, NC to Durham, NC. All of it on 4 lane interstate or larger freeways. I got the cruise control set on 73 mph, and was in the second lane in from the left hand fast lane. So the lane was probably worn in good. anyway, my mileage was fluctuating between 56.1 and up to 73. I don,t know if I had a tail wind or what.

    Anyway, on the way back this evening I tried the same thing again, 73 mph on cruise, and left hand fast lane, one in. Again, I averaged over 60 mph. when I finally stopped for gas, I had two pips left, and 483 miles on the tank and an average of 51.0 for the tank. (I was two pips down when I left here, but that's included in the 483 miles).

    Anyway, just thought I'd post to see if anyone else has had any similar experience? No bad mileage for 73 mph, huh?

    :D
    RD
     
  2. spitinuri

    spitinuri Member

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    I can never get better than 50 mpg running at 70 mph. Good job.
     
  3. swich2mac

    swich2mac Go Hard or Go Home!

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    How many gallons does the tank hold? I know, the math is easy but I wanted to know what the actual published size of the tank.

    Thanks,
    Scott
     
  4. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    The actual published tank capacity of the 2004 - 09 Prius is 11.8 US gallons.

    However, due to the emissions control bladder most Americans will never get that much gasoline in their tank.
     
  5. SureValla

    SureValla Member

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    I'm confused, you say you drove 73 mph but then in another sentence say you averaged over 60 mph. Which is it?


    I think it all depends on the road your driving to find a sweet spot.
     
  6. patsparks

    patsparks An Aussie perspective

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    Average speed is never as high as cruising speed as long as your cruise speed is also your maximum speed. You have to slow down for off ramps and stuff like that.
     
  7. Rangerdavid

    Rangerdavid Senior Member

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    Surevalla, thanks for catching the typo. It was 73 MPH and 60 MPG.
     
  8. Bob64

    Bob64 Sapphire of the Blue Sky

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    60mpg at 73mph is excellent.
     
  9. patsparks

    patsparks An Aussie perspective

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    David, you beat me, I can't match that.
     
  10. Frayadjacent

    Frayadjacent Resident Conservative

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    That fuel economy at that speed was probably more due to road conditions - tail wind, downhill, good road surfaces, etc - that contributed more than being in a functional 'sweet spot'.

    Regardless, it's a good number. I'd be happy!
     
  11. Tideland Prius

    Tideland Prius Moderator of the North
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    wow nice. At 70mph, I only get 47mpg (5.1L/100km). Could 73mph be the speed where MG...1?? disengages and the engine powers the wheels directly without sending anything to the battery? (I read something similar on Wayne's site....about how they can feel one of the MG's disengaging.. no idea how that feels/sounds like)
     
  12. Bob64

    Bob64 Sapphire of the Blue Sky

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    My only thought is: That must be one flat road...
     
  13. patsparks

    patsparks An Aussie perspective

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    My normal highway speed is 118km/h on cruise control and normally watch the MFD showing an average of 5.2L/100km on the highway. It's pretty flat round here.
     
  14. Rangerdavid

    Rangerdavid Senior Member

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    folks, I've had this Prius since august, 2006 and never gotten that kind of mileage before (well, not at highway speeds anyway)....

    I've made that trip numerous times before and gotten good mileage, but nothing that far above normal. I'm really happy. Jon, I think there may be a"spot" somewhere close to 73 mph where that happens. Maybe I found it by acciden!:cheer2:

    The real test will be to see if I can duplicate the effort when I make the trip again at the end of this week.

    :D
    RD
     
  15. patsparks

    patsparks An Aussie perspective

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    I just did some calculations.
    My normal highway cruise speed as I said earlier is 118km/h. I just did the conversion, 73mph! What do you know, snap! This gives me 5.2L/100km which translates to 45mpg US or 54mpg UK.
     
  16. a priori

    a priori Canonus Curiosus

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    I'd be pretty happy with mileage like that at such speeds.

    The only time I'd get really high mileage on an interstate highway (other than in construction zones!) is when there is warm (not hot) weather and the roadway is concrete or well-worn asphalt that isn't yet broken up. Such roadways are rather uncommon in the upper midwest!!
     
  17. darelldd

    darelldd Prius is our Gas Guzzler

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    I find that some days I get stellar, unexplained mileage. Then, doing the same thing in seemingly BETTER conditions, I can't touch that mileage. I think there's some hidden magic voodoo going on some days.
     
  18. a priori

    a priori Canonus Curiosus

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    I bet it's all in the spandex, Darell. Have you compared which tanks were winter spandex and which were not?
     
  19. Tideland Prius

    Tideland Prius Moderator of the North
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    Hmm... try 115km/h, 116km/, 117km/h, 119km/h and 120km/h lol... it might be somewhere in there.
     
  20. Mike Dimmick

    Mike Dimmick Active Member

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    You are aware of the Stage 3/4 transition? Once the engine is fully warmed up, it seems to need an idle speed check before it will run the engine at very low revs. It's aggressive about running it - it starts the engine when driving below the EV mode limit (I think - the original document says 34mph) and won't stop it. The engine goes into idle mode below 6mph, when slowing, and the speed check takes ten seconds. Some people advocate pulling over to allow this check to complete.

    (Idle check is my assumption based on the monitor for DTC P0101, which runs for 10 seconds when the engine is idle. I'm guessing it's calibrating the mass airflow sensor.)

    Annoyingly, on my commute, the engine isn't normally warmed up to 73°C before I get to the high-speed (60, 50, 40mph) section; once on the 40mph section there's a nice glide available with only occasional moderate input from the battery, which saves fuel, but the engine's gone cold again by the time I get to the next junction I might have to stop at. I normally get a chance to do the idle check only when I have a couple of miles to go, although at both ends of the journey there's a slow section followed by a fast section, then town traffic.

    Last week, though, temperatures were over 15ºC and I could tell the car was already in Stage 3 before the high-speed section, and I pulled over after crawling through the 20mph village. Result, pretty high mileage numbers, well over 75mpg 5-minute averages.