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Very low MPG for first 45 minutes, much higher after.

Discussion in 'Gen 2 Prius Main Forum' started by Soylent, Jul 21, 2010.

  1. Soylent

    Soylent The v isn't a station wagon! It's just big boned

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    I didn't know how else to word this, but I know that the Prius has a few "stages" it goes through as it heats up to a certain temperature and whatnot...

    Here's why I'm posting, in summary: I have a 2006 with 115K. When I was driving a 150 mile trip, for the first 30-45 minutes on cruise at 72mph, my mileage was very poor, much lower than average (40-42mpg). But after about 45 minutes, I slowed down for some construction area, then resumed cruising at 72mph, it jumped to about 48-49 mpg for the rest of the trip.

    For the first 45 mins, it felt like it was struggling, because I could feel like the ICE rpm's were higher than normal for that speed. I even tried to gun it to 80+ and coast down, but it still felt like it was working hard. Finally, when I slowed down to 60-ish, then sped back up, it started operating normally.

    Did that short slow-down force it into it's normal mode?

    Some details: I live in Florida, so it's 100% flat road, same highway all the way. It was 91 degrees the entire trip. I didn't change my A/C settings, or stop, or dump cargo, or do anything different.

    Any ideas?
     
    #1 Soylent, Jul 21, 2010
  2. richard schumacher

    richard schumacher shortbus driver

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    If the tire pressures were very low it might take them that long to heat up enough to get stiff.
     
    #2 richard schumacher, Jul 21, 2010
  3. ksstathead

    ksstathead Active Member

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    This observed behavior does not correlate with my understanding of the stages of warmup.

    Query whether all your maintenance is up to date? Transaxle oil change, plugs, pcv, sensor cleaning, etc.
     
    #3 ksstathead, Jul 21, 2010
  4. qbee42

    qbee42 My other car is a boat

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    Warm up doesn't take anywhere near that long. I am more likely to suspect external factors, such as road surface or head winds. Perhaps after you got through the construction zone the roads were better.

    Tom
     
    #4 qbee42, Jul 21, 2010
  5. Soylent

    Soylent The v isn't a station wagon! It's just big boned

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    So it isn't possible that it gets stuck in the warmup mode?
     
    #5 Soylent, Jul 21, 2010
  6. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Mine can take as long as 15 minutes, but is usually shorter in summer, longer in winter.

    Warm oil flows better than cold oil
    Battery completely recharges
    A/C catches up with demand
    coolant/engine block temps are up to operating ideals.

    If your thermostat was stuck wide open, It might take longer to get to operating temps

    http://www.samarins.com/glossary/thermostat.html
     
    #6 JimboPalmer, Jul 21, 2010
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