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Tire Pressure Surprise

Discussion in 'Gen 3 Prius Fuel Economy' started by geeter, May 8, 2010.

  1. geeter

    geeter Member

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    I just took delivery of my gen III last Friday, and have driven about 460 miles on the first tank of gas (still going :)).

    I went to run some errands today and the MPG's were not coming as usual. I have 57 MPG on the MFD for the tank and could barely creep into the 40's after about 10 miles.

    I decided to pull into a gas station and check my pressure. Sure enough, all four tires were at 22 psi. I couldn't believe they would be so low. I am assuming that the dealer didn't fill them up to spec (35 psi on the door label), but that is really low. I was impressed that I could still get 40 mpg with 22 psi, but I was none too pleased.

    I didn't check my psi during the week, as the car was new and I figured it was inspected (never trust the stealership, as I have learned before).

    So after all of my babble, I was wondering if the low resistance tires need to be checked more often (I have Ecopias)? I am a religious tire pressure checker (every fill up usually), but I hope this was just a case of the dealer not filling them up properly. Either way, I love the car thus far and can't believe how far I have driven on a tank of gas (never passed much over 400 miles in a tank in my life before).
     
    #1 geeter, May 8, 2010
  2. bisco

    bisco cookie crumbler

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    i lose between 0 and 2 psi per month. don't think it's any different from other tires. sounds like your dealer screwed up. sop!:cool:
     
    #2 bisco, May 8, 2010
  3. bruceha_2000

    bruceha_2000 Senior Member

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    If they were 22 PSI after running errands, they were a lot lower 'cold'.

    I think all tires (barring a known leak) can be checked at the same frequency. I generally do mine on Sat or Sun AM since I don't need to leave the house early.
     
    #3 bruceha_2000, May 8, 2010
  4. geeter

    geeter Member

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    Yeah, it reminded me why I always buy a car and never go back.... :)
     
    #4 geeter, May 8, 2010
  5. derkraut

    derkraut Member

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    I check my tire pressure judiciously once a month (I run with 40PSI, cold). I usually have to add 1-2lbs to keep them @ 40psi. For me, the difference between 30-40lbs psi is at least 3MPG. So, I don't mind the somewhat harsher ride.
     
    #5 derkraut, May 8, 2010
  6. stream

    stream Senior Member

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    Agreed.

    I've checked my cars' tire pressure monthly for as long as I can remember. First of the month, time to check tires. :D
     
    #6 stream, May 8, 2010
  7. GBC_Texas_Prius

    GBC_Texas_Prius Member

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    Dealers used to deliver cars with the lowest possible tire pressure because they wanted to impress you with a soft ride. I'm surprised a dealer would do that today after all the tire pressure accident publicity. Also, a Prius buyer is more focused on mileage any way.

    I'm with geeter. I'm seriously considering not using my two year "free" maintenance. About all I'll get out of it is one oil change and will get me in the dealer's service department database. I'd rather the dealer keep their hands off my car post purchase, even though they did deliver our Prius with exactly 35 psi in the tires. I bumped them up to around 41/40 and get increased mpg (lower 50's versus upper 40's) without a noticeable difference in ride.
     
    #7 GBC_Texas_Prius, May 9, 2010
  8. fuzzy1

    fuzzy1 Senior Member

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    Have you checked pressure with other gauges?

    22 seems low enough that you may notice it visually. Considering how many gauges out there are bad, I'd try multiple units to check whether most of them agree.
     
    #8 fuzzy1, May 9, 2010
  9. geeter

    geeter Member

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    I didn't check with another gauge, as I use a pretty decent digital gauge. It hasn't failed me before, but I should probably do that though.
     
    #9 geeter, May 9, 2010
  10. fuzzy1

    fuzzy1 Senior Member

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    If it is your own gauge that has been reliable on your previous cars, I would find it more trustworthy than a single random gas station gauge.

    I didn't wait for a gas station visit to check with my own gauges. Pressure was checked the morning after delivery, and found at 40 / 38 psi.
     
    #10 fuzzy1, May 9, 2010
  11. geeter

    geeter Member

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    I went to fill up tonight for the first time (500 miles, 54 MPG calculated) and pumped them up to 43.5/42 or so. I want to see the difference, and I don't mind the ride stiffness. I used to run my old VW GTI at around 40-42 all the time for MPG's. Thanks for your input everyone. :)
     
    #11 geeter, May 9, 2010
  12. JimN

    JimN Let the games begin!

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    The 1st thing I did when I got the car home was inflate the tires. The tp may have been in spec but was extremely low IMO. It took about a half hour to get all 4 tires up to 51.

    Just because the checklist says "inflate the tires" doesn't mean they do. My Intrigue was delivered to me without washer fluid. Some dealers will cut corners to save a buck. Some employees are slackers.
     
    #12 JimN, May 10, 2010
  13. Rokeby

    Rokeby Member

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    If the car left the dealer with only 22 psig in the tires and the TPMS
    wasn't in the alarm mode, doesn't that mean that it is set too low?

    Wouldn't it have to be reset below the standard on the door frame
    pressure? :confused:

    Now that would be a HUGE dealer screw-up in my mind. :target:

    If so, that's as far as I can go as I'm not conversant with the Gen III
    TPMS reset procedure.
     
    #13 Rokeby, May 10, 2010
  14. geeter

    geeter Member

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    Thats a good question. I am not familiar with the TPMS procedure. Can I set it myself, or do I need a OBD hookup? With my old VW, I needed a VAG-COM to do most of those types of things.
     
    #14 geeter, May 10, 2010
  15. stream

    stream Senior Member

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    During PDI, the dealer needs to activate the tire pressure sensors, then initialize the system. I've posted the TSB a few times, most recently within the last week or so, so try a search if you're interested.

    After that, whenever you change the tire pressure, you need to re-initialize the system (instructions in owners manual).
     
    #15 stream, May 11, 2010
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