New Tires Lowered MPG UNTIL...

Discussion in 'Gen 4 Prius Fuel Economy' started by Flo Samuels, May 1, 2019.

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  1. Flo Samuels

    Flo Samuels New Member

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    My son drives a 2017 Prius. I drive a 2007. For both cars the mpg were 46.something until we got new tires. My son's mpg dropped to 37, mine dropped to 41. Both the new tires were from Discount not the brands that were on the cars.

    Now here is the kicker. My son took his into the dealership, they had it a week and no fix. He said in a survey he would never recommend the dealership to anyone. In fact he would ensure no one went to it for a Toyota. So the service manager drove the car, they had it for a day and suddenly the mpg were back to 46.something.

    My question is pretty simple. What could they have done to my son's car to fix the gas mileage issue? It obviously has to do with the new tires. And is something I want done to mine.
     
  2. alanclarkeau

    alanclarkeau Senior Member

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    New tyres need running in - but only 500kms I think.

    Do you keep accurate records of your fuel use - or just the dashboard display which is only a calculation from a number of sensors, and sometimes errs considerably?
     
  3. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    The type of tires is most important. Low rolling resistant tires will help get better mileage - sticky or winter tires will hurt. Run-flat tires are especially bad delivering economic good news...
     
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  4. alanclarkeau

    alanclarkeau Senior Member

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    I didn't realise that run-flats were worse - I've seen them on cars which I wasn't really considering. But it stands to reason, they're usually on prestige or sporty cars.
     
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  5. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    Especially heavy.
     
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  6. The Professor

    The Professor Active Member

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    Tyres can and do affect fuel use.

    But, if the dealer is using the same tyres at the same pressure, and gets different MPG than you, then it's likely down to one of the numerous factors that could on their own, or combined, easily make the difference you're seeing.

    These include driving style, the music you're playing, your mood, wind direction, wind speed, temperature, humidity, wet or dry roads, traffic conditions, battery level at the start and end of the journey, and of course tyre pressure and types. Most of these are really hard to control for.
     
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  7. PosauneGuy

    PosauneGuy Member

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    Did you check the tire pressure before and after the service visit? (When I purchased my 15 Prius, I was getting low-40s mpg while my 11 Prius regularly got low-50s.) Couldn't figure out why the new car had such poor mileage. Then I checked the tire pressure and the pressure on the new car was around 30 psi. Brought those up to 40/38 and mileage was up to high-40s/low 50s.)
     
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  8. sam spade 2

    sam spade 2 Senior Member

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    My answer is pretty simple:
    Maybe you should ASK THEM instead of speculation and guessing in a place like this.

    Then......what appears to be the obvious conclusion is sometimes dead wrong.
     
  9. kithmo

    kithmo Couch Potato

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    As said above, probably the dealer upped the pressures (and then did a few doughnuts around the car park to bed the tyres in :whistle:).
     
  10. a_gray_prius

    a_gray_prius Rare Non-Old-Blowhard Priuschat Member

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    Did they do an alignment? Do you know what the alignment values are on your car?
     
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