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My gas mileage has dropped from 50 to 43

Discussion in 'Gen 2 Prius Main Forum' started by remax, Jun 7, 2008.

  1. remax

    remax Junior Member

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    Could this be because the weather. It is real hot and humid, running a/c alot. I drive an 07 with approx 10k on it.
     
  2. Sheepdog

    Sheepdog C'Mere Sheepie!

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    whats the tire pressure like? Is your gas E85? Shorter trips maybe? A lot of variables
     
  3. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Yeah, lots of variables.
    You mention the A/C running. Even though the A/C is not mechanically connected to the engine, it does affect your mileage. The electrical draw of the A/C will deplete your hybrid battery faster which will cause the engine to kick on to recharge it. The only time A/C has a near-negligible impact on mileage is steady driving on the highway where the engine is running anyway. But since I don't drive highway often, I notice a big difference in stealthing and gliding distances when I have the A/C on. This, of course, lowers my mileage.

    Also, is this a trend? Did an entire tank go by with the lower mileage? I ask because sometimes someone posts a similar question and it turns out they just a really bad single trip. Or as my Statistics professor used to say, conclusions can't be made on a single data point.
     
  4. remax

    remax Junior Member

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    This is my first tank that has done this. Now I have always pretty much been by myself or one passenger. Could the fact that I was driving 4 passengers make that kind of difference. My air pressure is 40lb all around.
     
  5. qbee42

    qbee42 My other car is a boat

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    Four passengers will make a difference. With one tank there can be a lot of other variables, such as getting a bad tank of gas. Don't panic yet and give it some time.

    Tom
     
  6. patsparks

    patsparks An Aussie perspective

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    Can we also make the assumption that you were not driving your normal commute if you did not have the normal number of people in the car?
    If you include more higher speed highway driving, ethanol fuel, more air conditioner use, more weight, more hills, or more wet roads you will incur an increase in fuel consumption. When you combine 2 or more of these circumstances the affect is compounded. Even the road surface can have an affect.

    See how the next tank goes.
     
  7. remax

    remax Junior Member

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    Thanks guys I will monitor the millage, hopefully the fuel is the culprit. I will report back next tank.
     
  8. Rokeby

    Rokeby Member

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    Yesterday, I had a new owner's wake up call myself. Temp was 100 deg F,
    humidity above 90%. (I've read that humid air is less dense than dry air. It
    sure didn't feel like it though.) Had parked the car in the open, it was hot
    as an oven, even though I have the front/back window sun deflectors, and
    cracked the windows.

    I got 57 MPG over the 7.7 mi. trip to work. In that distance I drop down
    some 350 ft. in altitude. On a good day --light traffic and some luck with
    traffic lights -- I can get home at 5 MPG less that the outbound trip, in this
    case 52 MPG. BTW, this is all city driving.

    When I started the car, I remembered that I'd read that the HV battery
    works best at temps we humans like; warm in the winter, cool in the
    summer heat. So I set the A/C at 78 deg., Auto, and expected a MPG hit.

    But, Oh! What a hit! Got home at 44 MPG.

    For most of the trip the A/C fan was running halfway between Med and High.
    At stop lights, the ScanGauge said the ICE was stopped, yet there was
    mechanical noise from up front, which I take to be the A/C compressor.
    Most of the way the H/V battery gauge was at 4 bars, occasionally 5, when I
    usually see 6 pretty much all the time.

    So, it looks like I'll have to get used to a new-for-me hot weather reality.
    MPGs in the mid 40s as opposed to mid/upper 50s that I've enjoyed for the
    past two months. I guess my smugness factor takes a hit too.

    Life goes on.
     
  9. richard schumacher

    richard schumacher shortbus driver

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    Mid 40s is still better than the vast majority of American cars under any circumstances. Be happy.
     
  10. problemchild

    problemchild New Member

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    AC knocks mine from 51+ to 45+ so yes its the ac. When you have a motor the size of a golf ball any extra load will punish mpg. Its not like a GM Tahoe where AC makes little or no difference.

    I installed roof racks and went from 51 to 28mpg.
     
  11. tajohns

    tajohns New Member

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    I have experienced a similar problem with my '07. I was averaging 48- 50 mpg, then one hot day, it felt like the engine was doing all the work when I was in stop and go. My tank was at about 1/3 to 1/4 full and by the time I filled up, my average had dropped to 45 without changing any driving habits.

    After I filled up, I've been struggling to keep a 45 avg. It really seems that when I start, my engine has been taking the brunt of the power. My readout says between 9 and 20 mpgs until I get to speed. Of course downhill is still 99.9, but does anyone have that kind of experience during hot weather?

    My tires are 42 front and 40 rear and it's just me by myself or me and my wife in the car.

    I'm almost ready to take it in to the dealer and see if there's a problem.

    Oh, and at what speed does it typically take before the engine starts in? I have to really baby it to get to 5 mph and if I'm going downhill, 10 - 15 mph.

    Thanks for any input. :)
     
  12. richard schumacher

    richard schumacher shortbus driver

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    This does not sound unusual. I'd say save yourself the trip to a dealer.

    Uhh... was the sudden change co-incident with getting it serviced?
     
  13. hobba

    hobba New Member

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    I have experienced a sudden and unexpected loss of mileage as well. Almost 10 MPG which lasted over a month. I took it to the dealer and they ran a fuel consumption test. For an 11 mile test the car avg. 54.9 MPG. They felt the electronics were wrong and the car was producing the right mileage. They reset something in the electronics, and the MFD returned to displaying the accurate mileage. However, after a few days, the MFD again shows a low mileage figure. Its going back in on Sat. and they will contact the Toyota Tech Line to get some guidance on why this is happening.
     
  14. skguh

    skguh Member

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    That's my experience. It got HOT (upper 90s) the latter part of June down here (Alabama) and my driving habits had to change. I also put up a screen in the windshield and leave windows cracked for air to escape, because the A/C makes every effort to get the cabin temp fixed ASAP according to the climate setting. I also increase the thermostat (set on aauto) to 77 or 78, 'cause when it's 96 degrees, 77 feels cool. Plus anything else may affect the traction battery cooling (as I understand it).

    I have to change my driving style, relying on the used of the ICE more to charge the battery as the A/C really sucks the energy. It's when it's hot like this that I switch to the interstate, or long runs over 40 MPH with the cruise on. Lot's of stops and starts, heavy slow traffic that might usually be beneficial, suddenly became my enemy.

    Hope this helps. You can e-mail if you want--I'm down in MGM.
     
  15. tajohns

    tajohns New Member

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    Nope, haven't been in for service. Might be like what hobba was saying. I got about 485 miles out of last tankful. I'll see how it goes on this tankful and over the summer before I think about taking to dealer.
    Thanks for the input.
     
  16. Genoz World

    Genoz World ZEN-style living

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    yep people - getting hit also. but instead of getting VERY good mileage like you guys, 48-50+, i've always gotten a consistent 47.7.

    i recently added TOURING rims and BRIDGESTONE POTENZA'S and the mileage went down to 47.2 - that's with the addition of the air con and the tires/rims.
     
  17. YoDaddyAlex

    YoDaddyAlex Member

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    i cannot get into the 50s no matter what i do. ive always hovered around 45-48
     
  18. MaulWalker

    MaulWalker New Member

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    On a trip out to the country for a July 4 party, I noticed that my MPG wasn't as high as I am used to/thought it should be. When I got home, the first thing I checked was tire pressure, although I had just checked the pressure two days ago. In that two day period, I had picked up a screw in my right rear tire dropping the pressure from 40 psi to 36.5 psi. In that short amount of time, I dropped about two MPG.
     
  19. a priori

    a priori Canonus Curiosus

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    Going from one person to four and adding air conditioning can make all the difference in the world.

    Just two weeks ago I had an opportunity to run a rather unique experiment. On Tuesday I drove from Chicago to St. Paul, returning on Wednesday. I drove this leg alone, no A/C (for the most part) and very few interstate miles -- mainly U.S. Highways and four-lane divided State Highways. I also drove many of the miles in the evening and night-time hours. On Friday of the same week I drove nearly the identical route from Chicago to St. Paul, only this time I took the rest of my family (4 total) and a bit more luggage. I drove with the A/C on Auto (78) the entire time, and I drove a few more miles on the Interstate (the return trip on Sunday had no Interstate miles except for about the last 50). Most of the hours driven on the second trip were daylight, warm-temp driving times.

    What a difference in mileage! The first trip included a tank of 601 miles and 60.5 MPG. The second trip averaged out to about 53 MPG. The only saving grace that kept the second trip above 50 is that I drove many miles in hilly MN/WI manually. I would coast down one hill going as fast as 65 - 70, while slowing down on the upslope to as little as 45 (unless there were cars behind me). For many of those sections I could keep above 60 MPG even with A/C on!

    So -- A/C will create an MPG hit, but so will weight! Also, interstate driving at 65+ will absolutely kill mileage. At that point, the A/C doesn't make that much of a difference. If you are driving around town at 35 to 45 mph, then A/C will rob you of MPGs (even if it does make you comfortable).

    For the two trips, I was happy with the great mileage on the first one, and I was happy the family was comfortable on the second trip.
     
  20. unigeezer

    unigeezer Member

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    I just bought a 2004 package 5 with 70k miles from a toyota employee. It's been serviced like clockwork and on my first fill up, and at the 200 mile mark, the MFD indicates I'm averaging 64mpg. Yes, I reset the odo when I filled up. Is this considered pretty decent, run of the mill mpg?

    I also drive as usual and don't really try to drive any more conservatively than I did with my honda crv. I'm pretty heavy on the gas pedal lol. I also drive up hill quite a bit. I'm a little disappointed that I'm not getting better mpg with all the talk lately about getting 100 mpg or more. But if I'm getting more than 700 miles per fillup I guess I can't complain too much. :)