Lower fuel economy - Higher Battery Charge

Discussion in 'Gen 2 Prius Fuel Economy' started by NotJustZero, Dec 16, 2007.

  1. NotJustZero

    NotJustZero New Member

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    I am new to this forum, but am hoping that someone can help me. I have browsed the other threads, but am not quite finding the answer to my circumstance.

    I have a 2007 Prius which has about 7,000 miles on it. For the first 5,000 miles or so, I was averaging about 46 mpg in mixed driving. I took it in for its first service and after that have been consistently getting lower mileage - not even able to break 40 mpg in mixed driving. I am currently averaging about 35 mpg on the current tank of gas and the thing that I notice is that the battery seems a lot more fully charged than it used to be. I have taken it in to the dealer, but they say everything is working normally and they cannot find any faults. I have read the discussions around cold weather impacts, but this is Seattle we are talking about and not Chicago. The temperature is currently 46 which is certainly cooler than before, but for a 25% hit on fuel economy...

    :eek:

    What I have noticed on the consumption screen is that the gas engine comes on even when the battery is close to fully charged (with green bars) even when the car has warmed up. Before, when I would park and leave the car on, the battery would drop down to the purple range before the engine would kick in. These days it barely drops out of the green bars. My layman observation is that there is some sort of switch that kicks the power coming from the batteries or the engine and this is not precisely calibrated - I would imagine that this calibration would be similar to tuning the engine of a car where the idling kept it running smoothly, but not revving too high. I feel like the dealer has "tuned it" to a non-optimum level.

    Do you guys have any thoughts on what the issue could be or what I can do?

    Your thoughts are much appreciated!
     
  2. efusco

    efusco Moderator Emeritus
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    This is a cold weather phenomenon. The ICE must run a lot more to keep itself and the cabin warm...warm-up takes a lot longer. While it's running to produce heat it's also producing extra power that ultimately gets dumped into the battery. The ICE comes on quickly, in part, b/c the battery is also cold and not as able to deliver power as when it's warm.

    If this bothers you a lot and you want to get better FE you can do a few things. Best, if you can, is to install an engine block heater...this will prewarm the ICE and help shorten up that warm-up period dramatically. Next, try keeping the climate system set on manual (AC off and Auto off) on max cold setting for about the first 5 minutes. This keeps cold air from circulating around the ICE and allows it to heat up more quickly. After that first 5 minutes you can turn the temp up...I usually go with something like 67-68 degrees.
    Also, many of us have our grill blocked (see Knowledge Base forum for articles on grill blocking and engine block heater)...this keeps the cold outside air from getting through the grill and cooling the ICE while driving and thust prevents it from needing to run so much just to keep itself warm.
     
  3. patsparks

    patsparks An Aussie perspective

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    Thanks Evan, I was going to say heater or climate control.
    Tyre pressures also and check oil level. I hope the service tech used the right low viscosity oil.
     
  4. icarus

    icarus Senior Member

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    Ditto what Evan says. I am in Bellingham and have had my grill blocked (all but the bottom slat since early November. It has kept the mileage up. You'll notice a mileage hit very quickly if you don't block the grill and you are trying to run any heat.

    Good luck,

    Icarus
     
  5. NotJustZero

    NotJustZero New Member

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    Thanks all for your prompt responses! I am going to try both the block and the turning the AC setting off for the first 5 minutes and see what that does.

    Based on the responses here, I am guessing the battery staying highly charged is not a matter of concern you guys would see here. Correct?

    The dealer also said something about oxygenated fuel causing a drop in mileage. Anything to this from what you guys know?

    Thanks again!
     
  6. john1701a

    john1701a Prius Guru

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    Beside the inevitable negative effect cold temperatures and winter-formula fuel have, the dealer likely contributed to the lower MPG too.

    Check your tire pressure. Higher is better. 35/33 (front/back PSI) is the absolute minimum. I prefer 44/42. Many here use 42/40.

    Oil is likely overfilled. Above the "full" mark is a complete waste, and extra unnecessary internal drag. It extends the engine warm-up time too, since there's more to warm-up. About a 1/4-inch below that top mark is ideal.

    First time tire rotation is nothing you can avoid. You just have to endure the miles it takes for those former back tires to adapt to now being in front. Once they wear down a little, MPG won't be impacted as much.
     
  7. burns_fisher

    burns_fisher Burns

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    Very suspicious that your MPG suddenly got worse after a visit to the dealer. Here are some random ideas:

    Did the dealer per chance reset the MPG display, and is it this indicator you are relying on. If you had not reset it since buying, any change in the actual MPG is reflected slowly on it, so you might not have noticed as the MGP went down with cooler weather. If the dealer reset it, you suddently see the real MPG. But in the 30s? What kind of driving do you do?

    Your mention of the A/C makes me wonder: Do you have the A/C on? Are you running with defrost a lot of the time? Above 33 or so degrees, the A/C compressor will run at least some of the time with defrost on if you have enabled it. By default (setting Auto climate control) the A/C is enabled. The dealer might have messed with that setting if it is not something you touch much.

    Generally, this is a good thing. The A/C make for drier air blown on the windshield. However, you don't always need defrosting.

    OTOH, the A/C on this car is electric, so it does not contribute directly to having the engine run. It should just drain the battery more quickly (and thus force the ICE to run more often.)

    FWIW, I'm in NH where the temps have been in the 20s and 30s. (Ha...this weekend in the teens!) I got over 50MPH during the fall. Now I am getting in the low to mid 40s. My typical daily drive is about 15 miles each way over up-and-down back roads.

    You might want to try a ScanGauge or similar. Often looking at engine temp, battery state of charge, voltage, etc you can deduce why the engine might be running. (But sometimes not). It's pretty expensive if you would not have gotten it for anything else.
     
  8. Lumpkin owner

    Lumpkin owner Junior Member

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    I'm a new owner and just got on the website today. Lots of good info here. I just picked up a 2005 last Saturday and don't know a whole lot about hybrids. So tell me, why does the A/C kick in automaticly when you put the climate controls on "Auto"? Prob'ly a simple answer but not to me. Thanks.
     
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