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New Owner!!! ONLY 38MPG

Discussion in 'Gen II Prius Fuel Economy' started by Farias1109, Apr 29, 2012.

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  1. Farias1109

    Farias1109 New Member

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    Location:
    Bakersfield, CA
    Your Vehicle Year:
    2008 Prius
    Model:
    II
    I just bought my 2008 Prius a month ago!! Used 65,000k. So far my average mpg is 38! I usually pump 9gallons a tank, & it only last 350miles...? help please!!!

    What fuel economy are you getting and how are you determining fuel economy?
    38mpg. ONLY 350miles per tank

    - What fuel economy are you expecting and why?
    45+
    - What are the approximate outside air temps?
    70-100F
    - How long are your trips?
    25mins
    How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? I ran the test which on this form, and its all good.

    Have you had your alignment checked? Any pulling or abnormal tire wear? No & NO

    - How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving? 60mph. mainly highway.

    - What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.) flat/gentle hills

    - What are your tire pressures?
    51psi
    - Is your oil overfilled? (i.e. above the full mark on the dipstick)
    Full Mark


    - What region/state are you in? (if you haven't set your location)
    California/Fresno!
    - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking? normal. i dont excess 62mph+ and brake slowly...

    - Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on? No

    - Are you driving using D or B mode?
    D
    - HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to? AC/ LO!

    - Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15). i bought it used came with new tires...falken ziex ze 912 195 55 r16 87v
  2. Codyroo

    Codyroo Senior Member

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    Location:
    Pleasanton, Ca
    Your Vehicle Year:
    2010 Prius
    Model:
    IV
    The two obvious things sticking out are the tires (I don't believe these are Low Rolling Resistance (LRR) tires) and that you are running the A/C full blast (if it is similar to the gen III, setting the temperature to LO = full blast). The tires might account for 3 - 4 mpg. The A/C on full might account for anywhere from 5 - 10 mpg.

    F8L did a quick video showing the impact on instanteous MPG when the A/C was running hard and it was about a 10 mpg drop. As the car cools down, the MPG hit will be less as the A/C doesn't work as hard.

    But I agree, I'd expect 45+ mpg if I was keeping my top speeds to 60 mph and my trips were 25 minutes. The top speed limit will allow for very adequate freeway MPG (55+ mpg) and the 25 minute trips will offset the poor mileage shown in the first 5 minutes. Try setting your temperature to 74F and see if your mileage improves. You'll probably want to get the life of these tires, but realize you are trading fuel efficiency with tires that likely perform better in handling and stopping distances.
  3. uart

    uart Senior Member

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    Location:
    Australia
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A
    Hi Farias. You've got the "touring edition" which has slightly larger wheels and which most people (for whatever reason) report a few MPG less with (compared with the stock standard prius).

    I agree with codyroo that you're probably losing a few MPG with those tires. There's a bit less choice in LRR tires in that size, but there's definitely much better available than what you've got.

    Re the A/C usage. If you get a more humid type of heat in your location, try setting the A/C temperature fairly high, like about 75F, and just the drop in humidity will keep the cabin comfortable enough.
  4. jhinsc

    jhinsc Active Member

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    Just like any car, if you adjust your driving style, your mileage will go up. What were you driving before and what kind of mileage did you get?
  5. seilerts

    seilerts Battery Curmudgeon

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    Location:
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    Sigh. This answer provides no information. Many times, we have had people say the 12V is "good", when it was really bad. Give us real numbers, like 11.X at Ig-On. The value of X is important!

    Also, 51 psi is high for tire pressure, even if it is the max sidewall limit. You'll not see much of a MPG difference between 51 or 42 front/40 rear, but the comfort should go way up.

    Further things to check: Does the engine turn off when you come to a stop? Do you have a roof rack or anything else that would disrupt the aerodynamics?
  6. lamebums

    lamebums Member

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    Location:
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    Your Vehicle Year:
    2007 Prius
    Model:
    N/A
    Hi Farias1109--

    The biggest things that stick out to me are the touring wheels, the tires, tire pressure, and California.

    I've also got touring wheels and it can put a real dent in your highway mileage, although it doesn't matter nearly as much in the city. I have to work hard to get any 60+ highway segments and that's by barely holding 55 MPH, sometimes dropping slightly when going up hills (52, etc.). On the plus side, your car can be easily distinguished from a Prius with standard wheele.

    With regards to the tires, I agree with codyroo and uart - LRR tires would help here. With tire pressure on the other hand, I have to respectfully disgree with the others. I firmly believe that PSI = MPG, and I believe everyone should press up their tires to the maximum pressure listed on the sidewall.

    I can't officially recommend you go over sidewall, but I can personally say I run mine at 60 PSI, which I may lower because if I keep it up I'll damage my spine before long. I've driven in a Prius with the tires as high as 80 PSI before without any ill effects except the TPMS light being on and the CD player skipping every time you hit a bump. Tires can take a lot more than we give them credit for, but mercifully it wasn't my Prius - or my tires I was paying for.

    Lastly, living in California means you get CARB-compliant gasoline mixtures - since they banned MTBE a while back, the only way to get the fuel oxygenated enough is to add ethanol to the fuel. E10 in my experience with the 1NZ engine series can cost you up to 15% of fuel economy :mad:
  7. ItsNotAboutTheMoney

    ItsNotAboutTheMoney EditProfOptInfoCustomUser Title

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    2010 Prius
    Model:
    II


    It may be obvious, but that could be added to the questionnaire.
  8. seilerts

    seilerts Battery Curmudgeon

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    If you could give us some idea of what to expect in a Touring at 60 mph, for 40, 50, at 60 psi, tat would be helpful. I personally did not find any benefit from running mine over 42, but I have LRR on 15s.
  9. Southern Dad

    Southern Dad Active Member

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    Location:
    Monroe, GA
    Your Vehicle Year:
    2011 Prius
    Model:
    Three
    When I had my 2008, I found that my speed had a lot to do with my mpg. Like you I ran air conditioning all the time. My average was 44.4 mpg over the six months. http://www.fuelly.com/driver/southerndad/prius. I tried several different things to increase mpg. I did have the low resistance rolling tires.

    I did successfully get higher mpg on a few tankfuls, but I'm too lazy to use the coasting method for long. I'd suggest checking out different ways for your commute. Maybe the terrain is part of the issue.


    Sent from my iPad using Tapatalk HD
  10. ursle

    ursle Gas miser

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    Your Vehicle Year:
    2011 Prius
    Model:
    Four
    Second the speed, anything over 62mph is going to drop your mileage into the 40's, I also suspect the 12v battery, if the ice is running to charge a low battery @2amps, that's a lot of gas wasted.

    Clean your interior air filter, check your engine air filter, check your oil level, make sure the emergency brake is functioning properly and isn't binding the rear brakes, front wheel bearings ok?
  11. lamebums

    lamebums Member

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    Your Vehicle Year:
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    Hi seilerts--

    I'm pretty crushed on time over the next few days but I'll run a test of some kind later this week and I'll try to establish a decent set of controls in order to determine the actual mileage differences. My experience is largely limited to my prior vehicles: I do know I was getting under 50 MPG highway at 55-60 MPH when the tires were at 32 PSI all around, and now I'm closer to 60. But I'll keep you posted.
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