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Dramatic drop of MPG. Ideas?

Discussion in 'Newbie Forum' started by catlin64, Dec 10, 2011.

  1. catlin64

    catlin64 Junior Member

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    I bought a 2007 Prius 3 months ago. It was low mileage and for the first two months...GREAT MPG (average city/hwy of low-to-mid-50's). Since then the MPG has dropped to low-to-mid 40's. I have done two oil changes (one regular oil, one synthetic). The air filter has been changed. I have put new tires on the car (recommended by Toyota)...and had a sudden stop to miss a deer. It was immediately after the sudden braking that the MPG began to drop. The more after oil changes/filters...and finally tires. It's frustrating as heck. Ideas?
     
    #1 catlin64, Dec 10, 2011
  2. Dark_matter_doesn't

    Dark_matter_doesn't Prius Tinkerer

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    Check the 12 volt battery. If you do some reading on the Gen II forums, you'll find other accounts of owners resolving MPG drop-offs by replacing their 12V batteries.

    Optimus makes a very good replacement with battery posts customized for Prii.
     
    #2 Dark_matter_doesn't, Dec 10, 2011
  3. FLteacher

    FLteacher Junior Member

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    I bet it's the cooler weather and/or new tires.
     
    #3 FLteacher, Dec 10, 2011
  4. Dark_matter_doesn't

    Dark_matter_doesn't Prius Tinkerer

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    You'll also see the change from Summer to Winter gas formulation, and Winter gas can drop your mileage by 10% or more.
     
    #4 Dark_matter_doesn't, Dec 10, 2011
  5. xpcman

    xpcman Senior Member

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    Cold weather, winter gas formula and new tires all contribute to lower MPG. Those old tires where giving you better than average MPG. When you change tires (what brand/model are the new tires?) they take some time to break-in. I assume you are running the heater more with winter temps. That causes the ICE to run longer and use more gas.
     
    #5 xpcman, Dec 10, 2011
  6. cwerdna

    cwerdna Senior Member

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    #6 cwerdna, Dec 10, 2011
  7. richard schumacher

    richard schumacher shortbus driver

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    Short answer: colder weather. It hurts all cars, it's just more obvious in a Prius.
    Single best response: pump up the tires. You can go as high as the value shown on the sidewall. Tire pressures should be measured when the car has not been driven for at least an hour, and measured monthly or more often.
     
    #7 richard schumacher, Dec 10, 2011
  8. jbrad4

    jbrad4 Active Member

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    #8 jbrad4, Dec 14, 2011
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