milage drop by over 20%

Discussion in 'Gen 2 Prius Fuel Economy' started by dicklund2, Apr 17, 2012.

  1. dicklund2

    dicklund2 Junior Member

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    This Easter I put summer tires on my "new" (owned about 4 weeks) prius -07, and cleaned and greased brakes.

    With winter tires (almost new Nokia hakka xx, stud less) I got 4.5 l/100km (52mpg) easy and 4.2 (56mpg) at best, now I get 5.5 (42mpg) and 5.3 if I struggle, if I relax and put cruise control on I get 5.8 (40mpg). I travel 100km to work every day.

    Summer tires is Michelin primacy (about 2 seasons?) pumped to 3.0/2.8 bar (over inflated).

    Brakes don't seem hot after drive and they was really clean and easy to move after my service so my guess is that they work fine...

    Mileage went down over the weekend so I see a clear link.

    It was more fun trying to hypermile at 56mpg aiming for 60 then it is at 42 aiming for 45...:p

    12v battery charged, just in case. Still same temperature out 1-8 C. Oil and all filters changed first week (will change trans axle oil in summer).
    Travel to work got 4% shorter so tire size must be a small reason to the +20% problem.


    Well, does anybody have any ideas what I can do, what might happened?
    Primacy "must" be better then big soft winter tires.



    ---------------------------------------------------------------------------------
    - Have you read This Thead Yet?
    yes

    - What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
    trip

    - What fuel economy are you expecting and why?
    4.2-4.5 (52-56), got it before


    - What are the approximate outside air temps?
    2-7 deg. C

    - How long are your trips?
    50km x 2

    - 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?
    90% highway 100km/h, then 1km "city" at work parking lot

    - What region/state are you in? (if you haven't set your location in your profile)
    Sweden

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

    - Is your oil overfilled? (i.e. above the full mark on the dipstick)
    no

    How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)
    dont know age, 12,3 v after 2 days off

    Have you had your alignment checked? Any pulling or abnormal tire wear?
    no, no

    - 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).
    michelin primacy 195/55-16 (factory in sweden)

    - What are your tire pressures?
    2,8/3,0 bar

    - Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.)
    Jeep grand cherokee, 12l/100 km
    Volvo s80, 7,5 l/100km

    - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
    Let car decide, but try to get more electric near end of travel , "never" brakes

    - 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?
    18C (winter here), turn off heater at start of trip so engine stops at red light

    - If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute?

    Same commute, changed from good winter tires to good summer tires, fixed brakes
     
  2. GrumpyCabbie

    GrumpyCabbie Senior Member

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    If my quick google search is correct, then the Nokia Hakka Winter tyre is still a low rolling resistance tyre. If you have changed these to a non llr then you will see your fuel economy dive.

    Your findings all indicate to the new tyres. There are many threads on here about this issue. I had the same findings as you when the non llr version of tyres were put on my car. When these were eventually taken off the fuel economy went right back up to where it once was. I struggled to get 45 mpg US when I used to get 62 mpg US with ease and got again once llr's were put back on.

    Not sure what your solution is? Can you put the Michelins on another car or sell or just make do?
     
  3. F8L

    F8L Protecting Habitat & AG Lands

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    Part of the problem is the lack of an established pattern of mpg. You have only had the car for 4 weeks. That does not provide many data points! Regardless, I bet your problem is with the tires. New tires will always drop your mpg compared to a similar worn LRR tire. If you replace a LRR tire with a non-LRR tire or a marginal one then the drop will be even higher. Maybe you could list the exact tire you chose. Michelin Primacy what?
     
  4. Britprius

    Britprius Senior Member

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    I thought you worked in the UK Grumpy or are you buying your fuel in the US because it's cheaper.
     
  5. GrumpyCabbie

    GrumpyCabbie Senior Member

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    lol it just makes it clearer to quote US gallons and US mpg's on an American forum. Got bored explaining the difference so often :)
     
  6. dicklund2

    dicklund2 Junior Member

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    Thanks for answers!

    I belived that primacy was the model... but it also says XSE, there is no xse model that I can find. It must be a pilot primacy I guess? And you are right that is only a 8/10 at michelin energysaver indicator.

    Almost all prius I looked at had this tire, I read that it was as god as energysaver, but more models of primacy...

    I also saw that I had 2 Hakka H and 2 pilot primacy. The Hakka H claim to be LLR, but I can find very little information about it.


    BUT if I remember correct, best LLR tires save 5% fuel, how come that this tire that is "not bad" add 20%?

    Will look at winter tires for model in weekend, they are locked away for summer.

    It can't be possible that brakes is dragging along very little and makes milage drop but not adding heat to disc? Sounds impossible, but who knows...

    I must buy new tires for Volvo, but that is 15", prius is 16", to bad...

    (I calculated to US mpg)
     
  7. MalsaMikko

    MalsaMikko New Member

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    (hope my english is understandable)

    Similar findings here when changing from winter tyres to summer ones. (10% climb in consumption).
    Same thing in my former car VW passat.

    Little google and 20 year old belief turn to rubbish.

    I've allways believed that winter tyres roll heavier but it's the other way round.
    I'm talking about real winter tyres. Not these M+S winter tyres and those summer tyres like friction tyres they use in central Europe.

    At the end of this linked page you can see difference between studless winter tire and summer tire.

    nokiantyres.com/tyres-of-the-future

    I guess we only notice this at spring and fall because then we drive both winter and summer tyres in similar weather conditions.

    Those studless Nokian you have are one of the best rolling tyres money can buy.

    In my experience the differenses in rolling between winter nad summer tyres are greater than between two summer tire.

    Mikko
     
  8. dicklund2

    dicklund2 Junior Member

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    Thanks Mikko, it might just be that way, my winter tires from Finland are too good...

    I have to try change tires to Hakka Winter in june, just to see what mileage I can get then. Summer is coming in Sweden at temperatures of almost 15C and I can see better mileage even whit summer tires, Can't wait until it is steady at 20C and test if it really is a big difference even then.

    I have same "problem" whit my Jeep grand chreokee 4x4, much better milage at winter. But those Summer tires is really big (to big, but looks great) so I was sure that was the problem.

    Here is some direct links to test:
    http://www.nokiantyres.com/files/nokiantyres/muut_pdf/New_EU__tyre_regulations_3_2010.pdf

    Nokian Tyres - Summer tyres - Winter tyres - Friction tyres - Studded tyres

    I think I can understand that summer tire in test is Michelin energy saver.
    79 meters vs 129 meters.

    I want those Nokian prototype tires!
     
  9. Ansur

    Ansur New Member

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    Hi
    I have prius 2007 T4 its been really fine until last month i have always achieve 53mpg in and around London but suddenly it started running sluggish, i took it to Toyota and they recommended service which i did at the cost of 249 pound but this did not resolve problem engine was still rough and mpg dropped to 38mpg. Even i added fuel cleaner as well but no luck, now thats where the fun start one morning it refuses to start like no lights on dash i called AA all they did was checked battery and jump started car as per AA battery had 12.01 V and its fine but as per my research 12v battery must have minimum 12.8v to run prius at optimum. I replaced the battery just standard bosh s4 155 type cost 46 pound and waoo its like brand new car all sluggish gone and my 53mpg has came back and actually i see more time to time, so 12v battery plays very important role in mpg if your is 4 year old just dump it its a DIY job
     
  10. GrumpyCabbie

    GrumpyCabbie Senior Member

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    Hi Ansur, welcome to the forum. Yeah the 12v causes all sorts of issues when it fails. People assume it will fail in a similar way to any other 12v in a car but as it doesnt start the car it is hard to tell when it starts to go bad. Usually its around the 4 - 5 year mark or 70,000 to 80,000 miles.

    The 12v the AA were checking was probably coming from the inverter which charges the 12v in a similar way to the alternator on a traditional car. As the engine doesn't need to be running, people, the AA included, believe they're measuring the battery when they're just measuring the charge.

    The failing 12v is a very common issue which doesn't seem to have been picked up by UK Toyota dealers, but if you have any friends who have a Prius let them know as it'll save them a whole load of hassle.

    Whilst you're here, another good improvement to your car is to use low rolling resistance tyres when you next get some - they're not that much extra and really do work in saving money. Also, make sure your tyre pressures are spot on - 2 psi down and it'll seriously affect your mpg's.
     
  11. ProximalSuns

    ProximalSuns Senior Member

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    So I should see my mpg go up as the factory tires wear in? I have 1200 miles on the Yokohama Avid 33's that came on the Prius. Average 52 mpg.

    Planning on Nokian WG's for the winter and skiing (December-April). Nokian says they are low rolling resistance tires. Hope to keep the car to 50 mpg.
     
  12. dicklund2

    dicklund2 Junior Member

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    Thanks for all answers!

    Will get back when I try ed winter tires for test-run in summer, when that may come to Sweden, not yet anyway!
     
  13. F8L

    F8L Protecting Habitat & AG Lands

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    Yes. Rolling resistance is reduced as tires wear down. So mpg is usually increased over te lifetime of a tire. When you replace the tire you start all over again.

    The Nokians are an excellent winter tire. In fact, their Hakkapeliita tire (snow tire) is their lowest rolling resistance tire. Too bad summer temps would destroy them quickly.
     
  14. greengrasshopper111

    greengrasshopper111 New Member

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    I second the Nokians for winter. We even had those on a 96' Miata and that thing went through the snow like gang busters! Summer for the Prius.. i go with Hankooks from tire easy, they are a great value.
     
  15. rposton

    rposton Member

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    I have 321k+ miles on my '06. I have lost count, but I think it is on it's 4th set of tires.

    MPG has always been affected most by the weather. Temperature of the air, whether it is raining or not will affect mpg too.

    2nd most reason? Maybe tires. Not sure. Mpg does creep up a bit as I wear the tread off of the tires, and then drops when I put new tires back on, then creeps up as I wear that tread off and so on. Some tires have done better with mpg than others. My priority has always been wet road handling, not mpg. The tires I have on there now, are a little wider than standard, because there was no tire in the size I needed at the time i bought, and so mileage took a little hit on that. So right now I am averageing about 47 to 49 mph after the first 1000 miles of not pressing the reset button on the MFD.
     
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