Fuel economy dropping after tune up.

Discussion in 'Gen 2 Prius Fuel Economy' started by PriusHead05, Nov 6, 2020.

  1. PriusHead05

    PriusHead05 Junior Member

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    I got my ICE water pump replaced, the oil changed, and a tune up done. I needed a tune up as I noticed my MPG were dropping. First week or so the MPG was great! At around 50 mpg. Now the info screen still shows great gas mileage, but the actual number figuring I did when I filled up today, was 39. Why are my MPGs dropping again.

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  2. bisco

    bisco cookie crumbler

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    1) how many miles on her?

    2) are you following the maintenance schedule?

    3) what does a 'tune up' involve?

    4) how did you calculate 50 mpg the first week?

    5) what was it before that?

    6) what is info screen showing?

    7) you have a bladder which makes single tank calculation difficult sometimes
     
  3. PriusHead05

    PriusHead05 Junior Member

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    1: 138,000 mi.
    2: I just bought the car 3,000 miles ago.
    3: tune up involved changing the spark plugs, cleaning and reprogramming the throttle body
    4: screen data matched the math I did when I filled up. This time I filled up, the screen doesn't match my math.
    5: what is a bladder?

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  4. PriusHead05

    PriusHead05 Junior Member

    Joined:
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    Location:
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    Vehicle:
    2005 Prius
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    1: 138,000 mi.
    2: I just bought the car 3,000 miles ago.
    3: tune up involved changing the spark plugs, cleaning and reprogramming the throttle body
    4: screen data matched the math I did when I filled up. This time I filled up, the screen doesn't match my math.
    5: what is a bladder?

    Posted via the PriusChat mobile app.
     
  5. PriusHead05

    PriusHead05 Junior Member

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    5: when I got the car I was getting 39 mpg. After about 2 months it went down to 32 mpg. Got the tune up. Was getting 46~48 mpg. Now getting 39. (That is all true math I did.)

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  6. PriusHead05

    PriusHead05 Junior Member

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    6: screen info is showed currently 46 mpg. I reset the average mpg every time I fill up. I also noticed I get about 25 mpg the first 5 mins of driving. After that it's up to an average of 50 mpg.
    7: what is a bladder?

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    bisco likes this.
  7. PriusHead05

    PriusHead05 Junior Member

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    I also noticed that the ICE doesn't shut off until 5 seconds after I've come to a complete stop. The screen doesn't show the ICE running but I can hear and feel when it shuts off.

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  8. bisco

    bisco cookie crumbler

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    gen2 prius (2004-2009) have a rubber bladder inside the gas tank for pollution control reasons. it doesn't always expand and contract consistently, so the amount of gas you can put in at each fill up can vary, even when using the same amount.
    the best method is to keep averaging all your fill ups for a total average. you can look at fuelly.com to see what others are averaging.
    ice shut off has many variables and is not a good indicator of any possible problems unless it never shuts off.

    when you start out, the engine is cold, and burns more gas. as it warms up, it becomes more efficient. it is wise to combine trips when possible, going to the furthest destination, then working your way back.

    you can put your vin into 'toyota.com/owners' for the dealer maintenance history of the vehicle. if you have no other knowledge of past maintenance, you should read through the maintenance schedule at that website and complete anything not done.
    tire type and pressure can have a large effect on mpg, and it is also worth getting a free load test done on the 12 volt battery at most auto parts stores.
     
    dolj likes this.
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