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same trip, (nearly) same car, different MPG

Discussion in 'Gen 2 Prius Main Forum' started by camner, Aug 16, 2010.

  1. camner

    camner Junior Member

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    I've owned a 2007 Package 5 for 3 years, and just picked up a 2007 Touring Package 6. My wife and I drove it back from Portland (OR) to Tacoma, WA (about 190 miles) following each other closely. The trip ranged from open road (70mph) to stuck on the highway for a while (0-10mph). I tend to accelerate and brake more gently than she does, since I care more about MPG than she does.

    She got 52mpg in the original car, I got 48 in the new (used) Touring.

    Other differences: Original has stock Goodyear Integrity P185/65R15 tires inflated at 36-38psi; new Touring has new Yokohama Avid ENVigor 195/55R16 tires inflated at 32-34psi.

    Could/would the difference in tires and tire inflations account for a 4mpg difference on an identical trip?
     
    #1 camner, Aug 16, 2010
  2. kimgh

    kimgh Member

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    Possibly. I'd also consider things like break-in of the engine and drive train: the older car might win for that reason as well.

    Plus, there are probably sample variations as well. I'd actually be suspicious if you claimed you got the exact same mileage for both cars. A 4 MPG difference probably requires an explanation, but a 1-MPG difference would not, for example.

    This is my off-the-cuff opinion, backed by no knowledge or facts to speak of, so I defer to the more knowledgeable among PC-ers.
     
    #2 kimgh, Aug 16, 2010
  3. krg03

    krg03 Not expert, just experienced

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    Tire pressure and width and the driver will make the difference you saw. My wife gets better mpg than I do when she takes me to work (her car in the shop for a week). I let her drive me around aaaaanytime......
     
    #3 krg03, Aug 16, 2010
  4. cwerdna

    cwerdna Senior Member

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    #4 cwerdna, Aug 16, 2010
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, new tires typically yield worsened mpg even if air pressure is held constant.

    How closely did you follow each other and who was in front? Was the rear Prius close enough to benefit from drafting? ;)
     
    #5 Patrick Wong, Aug 16, 2010
  6. sktn77a

    sktn77a Member

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    Absolutely. We used to get ~50mpg with the original 185/65R15 Integrity tires. After switching to 205/60R15 Bridgestone Potenza RE960AS pole positions, our mileage dropped to ~44mpg. Inflations were about the same. The car handles much better but the mileage hit was significant.
     
    #6 sktn77a, Aug 17, 2010
  7. camner

    camner Junior Member

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    As always, I learn a great deal from folks here. Thanks to all for writing.
     
    #7 camner, Aug 17, 2010
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