10% drop in Prius v mpg after new tires and fuel injector service

Discussion in 'Prius v Fuel Economy' started by carlben, Mar 13, 2019.

  1. carlben

    carlben New Member

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    Vehicle:
    2016 Prius v wagon
    Model:
    II
    I drove my 2016 Prius v on a 20,000 mile trip to 30 national parks in 2017 and averaged about 42-43 actual mpg (I calculated it rather than just believe what the meter said which was 5% higher) even driving a lot in mountains, and that kind of acceptable gas mileage continued up until i got a 50,000 service, meaning I was getting up to about 45mp on average in optimal driving conditions, 41 mpg on on average at high speeds (70mph). The 50,000 mile service included putting on new tires (4 DT003-23460-YK-Yokohama Avid Ascend) which is what the dealer recommended, sizeP205/60R16 91H. I don't know the size of the original tires (I bought the car new). I have always kept my pressure at 35 front/37 back and checked in often. The 50,000 service also included a Fuel Injector and Throttle Body Service. Just after that I began another 10,000 trip through New England and the Maritimes of Canada and immediately noticed a substantial drop in gas mileage. I now was getting about 37mpg at high speeds and around 40 in optimal conditions, which has continued ever since. So at my next oil change I asked Toyota to figure out what had happened (i was now in Orlando FL, not the same place I had the 50,000 mile.) They said that they recommended a different Fuel Injector Service than the one I got at 50,000 mile and they thought might help - BG Induction Service, Clean Throttle Plate, so I had them do it. On the drive back from the Dealer, it did seem to help because for the first time since the 50,000 service ( according to the meter), I was seeing my mpg back where they used to be, but then it just reverted back to the lower mpg numbers the next time I drove. The Toyota dealer who did the most recent service said they could see no reason for the 10% fuel drop other than that the previous fuel injection service at 50,000 was not the one they recommend, which is why we did the second one. My driving now is 90% around town in Orlando. Very little high speed driving, and I am only getting around 40mpg actual mileage, if that. Any thoughts or suggestions. Thank in advance for any help.
    Carl
     
  2. hchu1

    hchu1 Active Member

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    Your OEM tires probably had a different tread pattern, but the size is the right size. Brand new tires will cause you to have lower gas mileage initially, they need to be broken in for best mileage. This could take over a 1k miles or more, but it certainly should be broken in by 10k.

    Your air pressure could be higher for better mpg, I have mine set at 44fr/42r. That's at the high end and will result in stiffer ride comfort. I have acclimated to this and it's a none issue. I get about 50mpg on the Bridgestone Ecopia EP422 I got from Costco.

    The fuel injector and Throttle Body Service I've never had from the dealership, so I can't speak to that item.

    Your drive pattern has also change from your previous pattern so that will have some affect on mileage. My driving is in the Houston metro area with a mix of freeway and suburban driving as a comparison.
     
  3. Rob43

    Rob43 Active Member

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    Model:
    Prime Advanced
    Drop In MPG:

    This is 0% fuel injection service related.

    This is 100% new tire related.


    Rob43
     
  4. bisco

    bisco cookie crumbler

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    the fuel injection caused an unnecessary drop in your bank account
     
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  5. Ronald Doles

    Ronald Doles New Member

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    There is a coast down test that was detailed on this site that gives you sort of a ball park for rolling resistance. You accelerate to 60 and then time the coast down. You repeat the test three times in each direction on a deserted highway. Too bad that you weren't aware of it and performed it on the old tires and now the new tires to compare the results. Just noticed that the original post was in March of 2019.
     
  6. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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  7. cnc97

    cnc97 Senior Member

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    Following for coast down test info.
     
  8. Ronald Doles

    Ronald Doles New Member

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    I did a search and couldn't find the link on this website to the coastdown test. Here is one from GrassRootsMotorSports that is also an Excel spreadsheet.
     

    Attached Files:

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  9. ETC(SS)

    ETC(SS) The other One Percenter.....

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    The station wagon Prius is rated for something like 43/39...so your mileages aren't that bad but the change is something that bears investigating.
    How many miles on the car in total?
    Have you ever had the brakes worked on?

    Advice:
    1. Your tires are inflated to spec but there are some in the forum who advocate bumping them up about 5psi. If you have a pump at the house, it will not cost you anything to find out.
    You might get some of the fuel efficiency back at the expense of a slightly harsher ride.
    As mentioned above, the -3 delta is almost dead-bang guaranteed to be the tires.


    B. I'm always VERY dubious about mechanics who prescribe car maintenance that's not in the warranty and maintenance guide.
    If you trust them, that's fine but you're probably over-paying for their "help."
    If you're close to your 120,000 maintenance then you may want to pay close attention to what they...ah....(*) "recommend" for maintenance.

    It would be a shame to save all that gas money only to have to give it back to a dealer for unneeded maintenance expenses.....;)
     
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