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Help me Understand

Discussion in 'Gen 2 Prius Fuel Economy' started by hdrygas, May 29, 2005.

  1. hdrygas

    hdrygas New Member

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    Help me understand want happened. I was running a very good tank for M.P.G. with the computer giving me a 54.5 M.P.G. after 3/4 of a tank. I am nearly at 15k miles on the car. I did switch gas to Chevron from Union 76. Last fill in typical Western Washington weather for this time of year on fill up and the first 3/4 of a tank. Cool lows in the mid 40's highs in the mid 50's and rain and on a few days unseasonable heavy rain. Then the weather turned clear and hot. Record hot. The lows were the same but the highs were in the high 80's and low 90's. I though good I may get a record tank here. Well my MPG plummeted to 49.6 on the computer. The am commute was not as bad as the afternoon. In the heat of day with traffic that was as bad it gets around here my milage was going down and down. I left the office and it was stop and go for the first 4-5 miles of the 17 mile commute. I set the air at 75 degrees, then turned it off, and the MPG went down. On fill up late in the day with the temp in the high 80's I pumped my first 10 gallon tank ever with 488 miles on the tank and a 48.31 m.p.g. calculated. Why? Should I have not done better as the temps went up? I am not figuring this out. I suspect the 10 gallon (10.101) is the bladder / temperature think but why the drop in m.p.g.? Help me figure this out. BTW after the tank fill the temp moderated to the 70's and I am running 55.2 m.p.g. on a very young tank.
     
    #1 hdrygas, May 29, 2005
  2. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    gee Henry, im getting strange readings too but in the opposite direction. im averaging 59 mpg by the pump but only 56 mpg according to the computer for the last 4 tanks in a row. my LT summer time average is now over the golden 55 mpg mark.

    i think your bladder did go through an expansion contributing to your 10 gallon tank. i have yet to pump 10 gallons. even on my last tank of 577 miles i only pumped 9.74 gallons. my biggest fill was last year of 9.87 gallons.
     
    #2 DaveinOlyWA, May 29, 2005
  3. hdrygas

    hdrygas New Member

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    I guess I would have expected to have gotten better milage when it got warm. I did go to a new station for the fill up so it could be a pump calibration. The pump was last inspected in 2000. However the car computer milage was going down. The traffic was as bad as I have ever seen it. We crawled for 3 blocks taking 5 light changes to go one block. Now that the temperatures are down I am now at 55.4 m.p.g. Go figure.
     
    #3 hdrygas, May 30, 2005
  4. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    using air?? as hot as it was, u b crazy if u didnt. if not moving much as in gridlock, that will definitely put a hurting on the mileage derby
     
    #4 DaveinOlyWA, May 30, 2005
  5. DanMan32

    DanMan32 Senior Member

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    My trips to work, when the air is cooler and the sun is still low (or down), I gain MPG. But on my trip home, my MPG suffers. AC has to work hard on my way home, both to cool down the already very hot cabin, and to combat solar radiation.

    As I stated in another thread, AC will eat battery power when running at high speed, and so the ICE has to make that up. If you're cruising, your SOC won't change much, but the MPG will go down a bit, but if you're doing more stop than go, then the SOC will go down, and ICE will run not to move you, but to maintain low SOC. Once you get moving, ICE will use part of its power to recoup SOC back to 6 bars.
     
    #5 DanMan32, Jun 1, 2005
  6. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    i agree with Dan... the only time i have ever been in the pink (2 bars) is when i had the air conditioning on and was sitting in traffic (averaging less than 10 mph, unavoidable full stops approx 50%) i saw the battery going down to 3 bars which i had never seen before and began to worry that something was wrong (had less than a 1000 miles on it and could have been much less)
     
    #6 DaveinOlyWA, Jun 1, 2005
  7. hdrygas

    hdrygas New Member

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    Well that describes the 3 days. I think next time I get into that I will bail and head out into the country. A few extra miles ,two sides of the square but open road. Traffic was ugly those three days.
     
    #7 hdrygas, Jun 2, 2005
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