Lowered MPG since major tune-up

Discussion in 'Gen 2 Prius Main Forum' started by drazoth, Dec 16, 2008.

  1. drazoth

    drazoth New Member

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    Hi fellow Prions,

    Was getting around 48/49, now since 20K check up/ tune up getting 38/39. Same driving conditions, etc.
    Any ideas.....?

    Thanks,

    MVL
     
  2. firepa63

    firepa63 Former Prius Owner

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    Check your tire pressure.

    What kind of "tune-up"? There is no tune-up for the Prius at 20K miles.
     
  3. Rotorhead

    Rotorhead New Member

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    At 20,000 miles the "tune-up" shouldn't consist of much more than an oil change and tire rotation.
     
  4. Celtic Blue

    Celtic Blue New Member

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    Look at the standard culprits for small changes first:
    1. Tire pressure--especially if you normally run something like 42/40
    2. Oil level--dealerships tend to overfill by 1/4"...sometimes dangerously more than that.

    How long has it been since the "tune up" and how much driving has been done since? Are you saying the mileage is down on the same tank of gas? The reason I ask the latter is because if the car was sitting and running at times during the work, especially with heat/defrost running (or AC during summer), you will have a low indication for the tank. If that is the issue then refilling and resetting the trip mileage counter will do the trick.

    The weather has changed in much of the country and it looks like Sausalito, CA is down 20 F on average over the last few months. That will impact mileage. Some of it is because the ICE will run longer to warm up. But some will also occur if you go from not using any heat or AC to using the heat or defog/defrost. Also, if tire pressure is set at a higher temp you should expect to lose about two psi just from the temp falling 20 F, and that will reduce mileage as well.

    Something else I picked up in another thread, but that you should probably wait for verification on from others here: Sometimes after maintenance or diagnostics the ECU's might have stored some inappropriate settings/ranges/calibrations that can effect mileage, etc. Some folks have reported getting their vehicle back to normal by removing the aux 12V terminal for a few minutes to reset the system to baseline. (If you do this, it is probably best to do it on level ground as there might be some sort of reinitialization of some levelling sensors as well, particularly with respect to the gas tank gauge--but I've not checked this to verify if this is a concern.)
     
  5. donee

    donee New Member

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    Hi All,

    Another issue is the wrong oil viscosity is sometimes used. 10W40 is reported reduce mileage compared the recommended 5W30.
     
  6. qbee42

    qbee42 My other car is a boat

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    Let me agree with the other posters: there is no 20,000 mile tune up. Look elsewhere for your mileage hit: oil level, tire pressure, temperature, dragging brakes.

    Tom
     
  7. Bob64

    Bob64 Sapphire of the Blue Sky

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    what'd they tune up?
     
  8. richard schumacher

    richard schumacher shortbus driver

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    In future consult the Toyota Prius Scheduled maintenance Guide that came with the car, or check here: Toyota Parts and Service
    The items shown there are the only maintenance items needed. Don't let a service writer sell you stuff you don't need. (Of course if during service they find something that's broken and needs repair, that's another matter.)
     
  9. mullins1975

    mullins1975 Junior Member

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    More information about what was performed in the tune up would be helpful. How many tanks have you gone through to get this new average mpg? As other suggested oil, tire pressure and weather conditions could all contribute. I would see how your mpg improves over your next few tanks, especially if the numbers are just from your first tank since the service.
     
  10. Celtic Blue

    Celtic Blue New Member

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    drazoth,

    Any updates? Have things improved? Were any of the comments on the mark/off the mark?

    Hope you have it worked out. (And for the record, my gas mileage is sucking with just the top grill blocked and temps in the teens on average. Mid 42 average on this tank for 2 to 6 mile trips--no long ones to help the average.)
     
  11. zak.kapoor

    zak.kapoor Junior Member

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    It is surprising that I had the same experience.

    I was getting 49MPG for the first 5K miles. After the first oil change it fell to 43/44. There was no other change in driving conditions.

    Yesterday the orange indicator (~!~) went on in the car. The manual said the tire pressure was low. I checked the pressure and it was down to 24.

    Let's see if the mileage goes back to 49 now.
     
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