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2002 Prius, Sudden MPG drop, 150k miles.

Discussion in 'Generation 1 Prius Discussion' started by Prodarwin, Dec 9, 2013.

  1. Prodarwin

    Prodarwin Junior Member

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    Vehicle:
    2002 Prius
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    Quick synopsis of issue:

    2002 Prius. 150k miles. Had the car around 1600 miles so far. Averaging low-mid 40s. 40-55mpg in town, and a solid, very repeatable 44mpg highway.

    Last night my GF and I drove back from NOVA/DC to North Carolina. We stopped at here sister's house along the way. Before stopping, the car drove as usual, delivering ~44mpg highway.

    After stopping, my GF drove while I napped for a bit. I woke up and stared at the MPG readout kinda funny... it had dropped down to 40.xx. Weird.

    We stopped for gas and I reset it. It consistently read 38-39mpg for the remaining 2-3 hours of our trip.

    Nothing has changed on the car recently that I can think of that would cause such a large sudden decrease. Oddly enough, the 44mpg was in snowy/icy conditions, and as things tapered off to rain, the mileage got worse.

    Because of the alarmingly low readout, I put the "energy" display on, and noticed that the engine was now charging the battery on the highway often. I don't know if this is normal behavior or not, because I almost never look at that readout on the highway, but it does strike me as odd.

    The only thing that jumps out at me is that this change in behavior happened almost EXACTLY after crossing 150,000 miles. The fuel up mentioned above occurred at 150123.

    No codes.

    Any ideas?
     
    #1 Prodarwin, Dec 9, 2013
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Not enough information to hazard a guess. But running the defroster is a stealthy hit on MPG. It runs the AC to de-humidify the air before blowing it on the windshield.

    Bob Wilson
     
    #2 bwilson4web, Dec 9, 2013
  3. Prodarwin

    Prodarwin Junior Member

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    Even with the A/C button off? I.E. the defroster will override me manually toggling the A/C off?

    Even then, 38-39mpg with the A/C on is pretty low, right? I've never seen this car sustain a MPG readout of <40mpg for more than the first 5 minutes of driving.

    Would this cable: Mini VCI FOR Toyota TIS Techstream V8 10 021 Single Cable | eBay (mentioned in another thread) allow me to check if any weird battery behavior is taking place but has not yet thrown a code?
     
    #3 Prodarwin, Dec 9, 2013
  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    If you're going after a miniVCI, verify they are an "Xhorse" reseller. "Xhorse" is the original vendor and getting the right one means having firmware 2.0.4 which also runs on the ZVW30.

    Bob Wilson
     
    #4 bwilson4web, Dec 9, 2013
  5. Jeff F

    Jeff F Member

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    Location:
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    Vehicle:
    2001 Prius
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    N/A
    Headwind. I always know which way the wind is blowing (I race sailboats!) and it has a marked affect on highway mileage. If the wind is strong, say 30mph, it can change highway mileage by 20% either way, depending on whether i's a headwind or tailwind. So I'm going to speculate that if you'd been driving in the opposite direction you would have been getting indicated mileage in the high 40s. Your comments about the weather support the theory. In fact if you passed through the front you could have gone from having a tailwind earlier in your trip to having a headwind in the latter part.

    A/C is automatically on in defrost mode, and definitely affects city mpg, but won't make any appreciable difference in highway mpg since the ICE is always running anyway. And the HV battery always bounces around between charge/discharge on the highway.
     
    #5 Jeff F, Dec 11, 2013
  6. Prodarwin

    Prodarwin Junior Member

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    Hmm, I suppose headwind is a possiblity, but we did stop for gas during that 3hr drive, and I would've definitely noticed a wind I'd think given the cold/rain temps.

    This is possibly related though... just on that last leg of the trip, the car developed a SMELL. Not noticeable when driving, but noticeable the next day unpacking, and tonight when I went down to vacuum/febreeze it. I got to thinking... the battery vents where? Outside the car? There are also some vents inside on the rear decklid as well, right?

    I think the rear decklid vents may have gotten covered (my GF put a sheet over the backseat to protect it from dog-hair as our dog was with is). Also, not sure if any venting is in the trunk, but the trunk was packed to the limit. The outside vent could have been frozen over with ice too.

    Now that the car is cleaned out and un-stinky I'll drive it to work again and see how its performing.
     
    #6 Prodarwin, Dec 11, 2013
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