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gas mileage difference

Discussion in 'Generation 1 Prius Discussion' started by ronlewis, Dec 3, 2019.

  1. ronlewis

    ronlewis Active Member

    Joined:
    Dec 5, 2016
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    Location:
    texas
    Vehicle:
    2001 Prius
    Model:
    One
    One of my cars doesn't seem to get the MPG as the others, according to the touchscreen meter. It even has a new rebuilt battery, no CEL, and runs fine. For example, I reset the mileage to zero, and start driving. The MPG number starts real low and slowly works its way up. Even if I do this after the car is warmed up, it does the same thing, starts off in the 20s.

    If I reset and get on the freeway, it'll get up to the low/mid 40s, so I think all's good, but today when I got in, I noticed it said 38 based on 2 miles driven. As as I started driving, it got all the way down to 31. I figure it's just because the engine is cold, but as I kept driving, i never did get it back to 40, even by trying to nurse it. Probably drove 5-10 miles, slowly, no freeway, and never did get over 40.

    I compare this to my other two. One is sitting at 48.4 based on 420 miles, mixed city/highway. The other has a dim screen, so I don't pay attention to it as much, and it's hard to see the numbers during the day, but they're in the mid-40s.

    The one getting the low miles did have a leaking injector oil ring. Actually had gas around it and could smell it inside. But I replaced that and don't smell it again. I'm going to check it again in the morning.

    My question: what are all the different things that can affect mileage in a seemingly good running car? Injectors I know. The throttle body looks clean. I'll hook up my ScanGauge to it tomorrow, but the SOC volts/percentage looked fine last time I did. What else can I check?
     
    #1 ronlewis, Dec 3, 2019
  2. ronlewis

    ronlewis Active Member

    Joined:
    Dec 5, 2016
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    Location:
    texas
    Vehicle:
    2001 Prius
    Model:
    One
    Occurs to me now that the alignment/something is a little off on this car. It's the one I replaced the passenger half-axle and wheel bearing a few weeks ago and it has a slight pull to that side...sometimes, at other times, it rides straight.
     
    #2 ronlewis, Dec 3, 2019
  3. fuzzy1

    fuzzy1 Senior Member

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    Location:
    Western Washington
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    Other Hybrid
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    Here is a list aimed at mainly new Prius owners, so don't bother filling out the questionnaire, but do scan the list. Unfortunately it doesn't cover all the old-car issues, but it is a start.

    Brake drag problems are clearly missing, but you can detect these from too-hot hubs.

    Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat
     
    #3 fuzzy1, Dec 4, 2019
    mroberds likes this.
  4. ronlewis

    ronlewis Active Member

    Joined:
    Dec 5, 2016
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    Location:
    texas
    Vehicle:
    2001 Prius
    Model:
    One
    thx
     
    #4 ronlewis, Dec 4, 2019
  5. Tscreener

    Tscreener New Member

    Joined:
    Feb 1, 2020
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    Location:
    Waterville wa
    Vehicle:
    2002 Prius
    Model:
    I
    I'm new here but o2 sensor could be an issue and still not set a code. An old sensor could be at the far edge of tolerance. The type and age of spark plugs also makes a difference.
     
    #5 Tscreener, Feb 2, 2020
  6. Josey

    Josey Active Member

    Joined:
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    Location:
    Virginia
    Vehicle:
    2003 Prius
    Model:
    One
    There are certainly plenty of things that can affect fuel economy, including the ones already notes (alignment, plugs, health of O2 sensors, anything that truly messes up the air/fuel mix...)

    But you can't really judge anything right after resetting the car's calculator. The 45-50ish mpg isn't a steady state thing. If you really want to bum yourself out, find a steep hill, reset to zero and drive up the hill. You'll likely end up in the 20s. But then if you want a thrill, turn around, reset it again and drive down the hill. I don't know if that display maxes out at 99 or not, but you'll likely get well over 100mpg. The # on the display is just a running average and I don't really see it as "solid" for about 1000 miles. Your actual mpg is constantly varying and there are plenty of things that affect it on a moment by moment or trip by trip basis.

    If I keep my '03 off of the interstates and do rural highway/town driving only I end up at about 53mpg (if I'm consciously trying to maximize without the more obnoxious forms of hypermiling). As it normally stands, most of my miles are interstate. In the winter I have winter tires on it (that are also 185s rather than 175s). Between the colder weather and wider/winter tires I'm down around 40-41mpg. The other 3 seasons with normal tires and warmer temps, that's when I'm at 46ish. (It seems that about 1/2 the winter loss is temps and the other half the tires as I delayed putting them on this season).

    None of that is any reason not to check things like plugs and wires though!
     
    #6 Josey, Feb 5, 2020
    dolj likes this.
  7. dolj

    dolj Senior Member

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    That right there is gold. Nice summary.

    Personally, I only reset the display if I am doing a specific test. Otherwise, it is only reset at every tank fill. I record all my fills as well, as this is a far better indicator of any change over the long term.
     
    #7 dolj, Feb 6, 2020
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