MPG drop after prepurchase inspection at Toyota Dealer

Discussion in 'Gen 2 Prius Fuel Economy' started by elephanyeyes, Mar 16, 2017.

  1. elephanyeyes

    elephanyeyes New Member

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    I just took a 2007 Prius that the previous owner's odometer read 300 miles and 42 mpg. On my test drive I reset the odometer and tested it with my driving and I was getting 50+ mpg around town. Then I took it to the dealer for a prepurchase inspection and when I got it back (and then bought it) it's been getting 28mpg in the city. This is with me driving 30 mph around town and not leadfooting it. Also, strangely when I switch to the energy view as opposed to the consumption view it shows me getting 40-55mpg while driving 30mph, not the 28mpg that it shows on the consumption view. I understand that the cruising mpg is not the overall mpg, but I'm not accelerating hard enough to warrant such a drop.

    So, could Toyota have done something on the inspection that would have messed up the fuel economy? the 12v battery is at 11.8v and they suggested I replace it asap. Thanks!
     
  2. CooCooCaChoo

    CooCooCaChoo Active Member

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    Did you check the 12v battery yourself or did the dealer check the battery? When its off, battery should read in the high 12.x range, and when running should read in the 14.x range.

    And yeah the 12v battery can cause problems if it can't hold a charge.
     
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  3. bisco

    bisco cookie crumbler

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    it's hard to gauge mpg's instantaneously. agree with above, test bad when cold, and replace if necessary.
    try resetting the trip meter and take a 20 mile drive under varied conditions, then see what the average is.
     
  4. uart

    uart Senior Member

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    Just drive it for a few tanks full and then reset the MPG and see how you go.

    There are several things that they could have done, none of them serious. They could have:

    - Had it idling in inspection mode for some time, which will serious impact the average MPG for a while.

    - Discharged and then force charged the traction battery. Similar to the above.

    - Had it sitting in accessory mode and let the 12V battery run down a bit. This can effect the MPG for a while. (Retest the 12V after a few weeks of driving)

    - Had the 12V battery disconnected which resets some of the calibration data that it uses to tweak the MPG calculations. This can effect the calculated (displayed) MPG for quite a while.

    None of these things are serious. At the worst the 12V battery might be have impaired a little, but it would have to be fairly marginal in the first place, so no great loss. Just retest it after a few weeks, it will probably be fine.
     
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  5. elephanyeyes

    elephanyeyes New Member

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    Thanks! Great answer!
     
  6. elephanyeyes

    elephanyeyes New Member

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    Would the top three explanations not affect highway mpg and only city mpg?
     
  7. bisco

    bisco cookie crumbler

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    i don't think any of us understand how you are reading mpg's.
     
  8. wjtracy

    wjtracy Senior Member

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    Gen2 12v batt discharges on sitting for weeks, there is a button under steering wheel to turn off SKS and help 12v stay charged on a Gen2. Gen3 it was done automatically (no button needed).
     
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