Hot weather + short (8 mi.) trips + blasting A/C = 35 MPG

Discussion in 'Gen 2 Prius Main Forum' started by SRQ, Jul 9, 2018.

  1. SRQ

    SRQ Member

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    Never had this happen before, but it seems like this car HATES hot weather. I remember last year seeing a Gen 2 broken down on the side of the road, and having a few issues like the ICE engine shutting off and throwing a red triangle. Went away after changing the oil, coolant, and cleaning out the mass air flow sensor, but the car's having a rough time at times again. Seems like it's wanting to turn the ICE engine right back on after it shuts down in order to keep power up to run the A/C. This really only happens when the A/C is running.

    Anyway, anyone else having weird stuff happen in the heat? My MPG bars go back to 45-50 after the warm up period, but by then I'm already home after stop and go traffic in the heat with the A/C maxed out.

    Perhaps a change in the type of oil?
     
  2. fotomoto

    fotomoto Senior Member

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    Your HV battery is 10 years old and not what it use to be in terms of performance. Electric air conditioning trying to cool down a hot cabin is a HUGE draw on the battery; a pack that is now both weak and hot so the ICE will run more to compensate.
     
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  3. bisco

    bisco cookie crumbler

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    how many miles on her? my daughters '08 with 112k is running fine, but we don't usually get close tp 100f.
     
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    My MPG bars go back to 45-50 after the warm up period, but by then I'm already home

    High temps, blasting AC, a mature HV battery and short duration trips that barely get the engine out of the warmup stage are the perfect storm for low MPG. Oil changes aren't going to help. Drop the AC from wide open to medium setting or a step or two under medium. Reduces the current draw significantly, but it just depends on what you want to sacrifice......mpg or cabin temp
     
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  5. srellim234

    srellim234 Senior Member

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    I spend a lot of time in the hot desert and you're right that the heat is tough on it but it's still better than just about anything else from the same time period. In 100* weather sometimes (not always) I just roll down the windows and put up with it if I'm only going a couple of miles or less around town. With the a/c on my average has been as low as 33 mpg. on a tank around here; otherwise it's about 40 mpg in the heat.

    On longer trips I use the a/c around half power and set to 75*. The average then is the low to mid-40s on the open highway at 70-75 mph. I'll be using it tomorrow when I run the 90 miles out to Palm Desert in the morning and 90 miles back around 2 in the afternoon.

    Still on the original HV battery pack and the car is garaged at home. I try not to leave it in the hot sun too much when it's parked.
     
  6. JC91006

    JC91006 Senior Member

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    AC use will decrease your mpg significantly. But even if it goes down to 35 mpg during hot weather, still better mileage than most cars out there. Just skip the starbucks for a day and blast the AC
     
  7. egg_salad

    egg_salad Active Member

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    Yup. this is my first summer with my Prius. Since I bought it, I've been getting 52-53 mpg. Now I'm getting 44. But it's been 110F out, mostly.
     
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  8. audiodave

    audiodave Active Member

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    After the car sits in that heat battery and inverter already hot. Wish I could run the battery fan with a charger and system off.

    Posted via the PriusChat mobile app.
     
  9. Starship16

    Starship16 Senior Member

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    I was only getting 16-18 mpg in my previous car. (I also do lots of short trips.) ANYTHING OVER THAT IS GREAT.
    It's getting very warm here in SoCal, and I run the AC every day. Mostly all year. I want to keep ME cool, and hopefully it helps the hybrid battery too. MPG is usually 54-56, and I don't care if it drops down to the 40s.:LOL: I don't get obsessive about the gas mileage... I just blast the AC at 65 degrees. :)
     
    #9 Starship16, Jul 10, 2018
    Last edited: Jul 10, 2018
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  10. WilDavis

    WilDavis Senior Member

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    I've only had my (2009 Gen II) Prius for about 4 years, and this current heatwave has been the worst for summer heat! I've noticed that the MPG always takes a hit if I need to use the A/C - the last few weeks in particular - high 40s for the past four or five fill-ups, diving down to 37.1 for the most recent (yesterday) fill-up (A/C on just about every time I drive recently (but A/C "on" is good for the TractionBattery :))
     
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  11. srellim234

    srellim234 Senior Member

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    A/C "on" is good for the traction battery but not if it's going to be on for about 7 minutes or less. That's why I don't bother if I'm only going a mile or two. It's physically impossible for that fan and A/C to actually drop the temperature of the physical components. It would be a lot different if the coolant were also flowing in and around the battery but a few minutes of cabin air blowing over it isn't going to help much.
     
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  12. SRQ

    SRQ Member

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    It has 191k on it.

    So I've been using a windshield cover and trying to park the car under trees and other shade I can find, and when I get in I immediately open all the windows to let the hot air billow out with the A/C on full blast. Once the A/C gets cold and the temperature equalizes with the outside air I seal up the windows.

    But these replies explain why my engine turns off and immediately back on: high power load and an older battery.

    Anyone know why my car would have thrown a red triangle and forced the ICE off, forcing me to coast on electrical power only to the side of the road last year? It happened 2-3 times. I pulled over, let the car cool a little bit, then started it back up with no issues. Only happened during the day during peak heat hours. Seemed to go away after I changed both the ICE and inverter coolant (they were due for their respecting 100k/30k changes anyway). I also cleaned up the throttle body, changed the PCV valve, and the oil, which again all seemed to fix the issue. Perhaps changing all of this stuff reduced the overall strain on the entire system below the point of the "straw that broke the camels back"?
     
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  13. bisco

    bisco cookie crumbler

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    sounds right, you probably hit it with one of those services.
     
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  14. SRQ

    SRQ Member

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    Did a long distance drive this weekend. MPG's returned to the normal 40-50 MPG range; posting for posterity.
     
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  15. hugoloveprius

    hugoloveprius New Member

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    I have same problem with error code P0A93
     
  16. dolj

    dolj Senior Member

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    Hi and welcome to PriusChat.
    I doubt it. Start your own post about your problem. Most likely the inverter coolant pump has failed.

    Search the Gen 2 forums, it is a reasonably common problem, and there are plenty of posts that have the information you need to sort it.
     
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