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Why is our MPG so different?

Discussion in 'Gen 3 Prius Main Forum' started by TheLos, Aug 19, 2013.

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  1. 3PriusMike

    3PriusMike Prius owner since 2000, Tesla M3 2018

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    Uh, not so quick. You might save $1000 if you really got a difference of 11 mpg. IMO, at best you are going to get 2-3 mpg difference from tires. You can probably get another 2-3 mpg by increasing the pressure from a low of ~34 psi to 42/40 psi. The other 5-6 mpg loss is still a mystery

    Mike
     
    #21 3PriusMike, Aug 19, 2013
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  2. 3PriusMike

    3PriusMike Prius owner since 2000, Tesla M3 2018

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    If only a tire change caused mpg to go from 51 to 65 don't you think:
    a. the tire companies would be advertising this left and right?
    b. a scientific analysis would be able to replicate this?
    c. pigs could fly?


    Mike
     
    #22 3PriusMike, Aug 19, 2013
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  3. TheLos

    TheLos Member

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    Hahaha so true! Most of August was unusually humid this year. I'm glad its almost over. I use "almost" loosely!
     
    #23 TheLos, Aug 19, 2013
  4. TheLos

    TheLos Member

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    Certainly something to consider! I've never traded in tires before, what kind of deal could I expect to get on the tires I'm trading in?
     
    #24 TheLos, Aug 19, 2013
  5. TheLos

    TheLos Member

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    #25 TheLos, Aug 19, 2013
  6. terry brecheen

    terry brecheen Member

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    Discount gave me 120 dollars for them. They had about 2800 miles on them.
     
    #26 terry brecheen, Aug 19, 2013
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  7. TheLos

    TheLos Member

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    Thanks Terry!
     
    #27 TheLos, Aug 19, 2013
  8. terry brecheen

    terry brecheen Member

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    My trip from work to home, 22 miles, i used to get 45 to 46 mpg. Five o'clock traffic is horrible here in houston. Today first trip home with new tires display showed 57mpg. I drove the same route, same driving style and same time of day. I didn't have any scientists waiting for me when I got home nor did I see any pigs flying but I know what kind of mpg I got with the old tires and what I have gotten so far with these new ones. I will take a 200 mile trip to Austin this weekend and post results. The best I've done previously was 49.1 & 50.0 on two previous trips. Have a nice day.
     
    #28 terry brecheen, Aug 19, 2013
  9. TheLos

    TheLos Member

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    Thats a fantastic outcome Terry! Great to hear it. Hope you enjoy that trip to Austin, I've never been but I hear its a great place. Looking forward to see your results.
     
    #29 TheLos, Aug 19, 2013
  10. terry brecheen

    terry brecheen Member

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    You are welcome.
     
    #30 terry brecheen, Aug 19, 2013
  11. vskid3

    vskid3 Active Member

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    I would still do what Vincent said and swap the tires between the cars to see what kind of impact the tires are actually having. Wouldn't want to buy new tires just to find out that there is another issue causing the lower mileage.
     
    #31 vskid3, Aug 19, 2013
  12. TheLos

    TheLos Member

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    Gonna do that this weekend!
     
    #32 TheLos, Aug 19, 2013
  13. fuzzy1

    fuzzy1 Senior Member

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    Yesterday, OP wrote:
    Have you done so yet? This is essential, don't be making tire comparisons until the pressures are verified as at or above the door label, and matched.

    What size and width are those Westlakes?

    Also, browse through the following questionnaire. This was not intended for your particular situation of two cars that ought to produce identical results, but it may help guide you to other mpg-related differences between them. Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new
     
    #33 fuzzy1, Aug 19, 2013
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  14. TheLos

    TheLos Member

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    I just got done checking the pressure. The tire pressure was different on each tire. I set them all to 40 and went for a 33.1 mile sample. 14 miles were on the freeway at 65-70 mph. Zero traffic. The rest was surface streets so nothing over 45 mph. Before adjusting the pressure my mpg's were at 45.1. At the end of the 33.1 miles I was at 55.7 mpg. What a difference!

    I ordered a tire gauge this morning and will be checking the pressure once a week. We've had our prius 2 for a month and this prius 3 for less than a week. I've learned a lot from this site already and appreciate everyone's knowledge. Even though this was solved by something which is probably obvious to most prius owners a lot of good brain storming was created and hopefully others will benefit from it.
     
    #34 TheLos, Aug 20, 2013
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  15. TheLos

    TheLos Member

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    Oh and the westlake tires are 195/65/15
     
    #35 TheLos, Aug 20, 2013
  16. 32kcolors

    32kcolors Senior Member

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    Hope you've controlled for other variables like starting with a cold engine because jacking up the air pressure alone does not cause a 10 mpg boost.
     
    #36 32kcolors, Aug 20, 2013
  17. TheLos

    TheLos Member

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    The car had been sitting for about 7 hours in the garage. The gas station where I added air is less than half a mile away. I started the 33 mile drive from there. It was probably about 83 degrees out at the time.
     
    #37 TheLos, Aug 20, 2013
  18. 32kcolors

    32kcolors Senior Member

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    I always find myself getting 5+ more mpg if I start with a warm or semi-warm engine so this is actually a large variable that must be accurately controlled for.
     
    #38 32kcolors, Aug 20, 2013
  19. TheLos

    TheLos Member

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    Im still very new to prius so I'm learning every day. I'll keep a close eye on the tire pressure and mpg's and see how it changes. I'll update info here.
     
    #39 TheLos, Aug 20, 2013
  20. 32kcolors

    32kcolors Senior Member

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    No problem. Here's an excellent thread on the Gen III warming up stages on which to educate yourself.
     
    #40 32kcolors, Aug 20, 2013
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