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Mileage Drop After Oil Change

Discussion in 'Gen 3 Prius Fuel Economy' started by Senior Chief, Jan 13, 2010.

  1. Senior Chief

    Senior Chief Junior Member

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    I've had my new 2010 Prius for three months. I've been getting 49.? mph indicated and 47.? mph in reality since I got it. Not bad considering most of my driving is Highway at 70+.
    I just brough it in for its' first Oil Change at 5100 miles. When the Toyota service advisor told me it was going to cost $68 if I wanted to continue to use the 0-20 synthetic, I opted out and decided on the 5-20 "regular" oil.

    Since the moment I drove off of the lot, I felt that the car was not "rolling or coasting" as well as it had prior to the oil change. Then I find that I now get 47 mph indicated and 45 mph in reality.
    Can the difference between syntheic oil and regular oil cause such a marked disparity, or should I be looking somewhere else?

    Thanks.
     
    #1 Senior Chief, Jan 13, 2010
  2. Paradox

    Paradox Prius Enthusiast / Moderator
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    I would have put the 0W20 since oil changes are 10,000 mile intervals now. But htat's just me, the car calls for it anyway so worthwhile to just put it. $68 does seem high though, I had mine done at the dealer and it was about $52 with filter, seal/ring, oil and taxes.

    Usually during oil changes they check your tire pressure and if high lower it. If you were running 'higher' than normal pressure for MPG's and they lowered it this could lower MPG. Also, if they overfilled it with too much oil, which happens to some at times, this too could reduce MPG. Also, using 5W20 over 0W20, although small, could lower MPG as well.
     
    #2 Paradox, Jan 13, 2010
  3. Tickwood

    Tickwood Active Member

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    I suspect that they may have lowered the tire pressures.
     
    #3 Tickwood, Jan 13, 2010
  4. paprius4030

    paprius4030 My first Prius

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    I thought synthetic was required for the 2010?
     
    #4 paprius4030, Jan 13, 2010
  5. spiderman

    spiderman wretched

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    0W-20 is required, just so happens that is only available in synthetic or possibly a blend.
     
    #5 spiderman, Jan 13, 2010
  6. msirach

    msirach Member

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    You need the 0w20 as recommended. Check the oil level since they may have overfilled it. It should be between the two marks.

    A drop in mileage after an oil change is usually due to them altering your tire pressure. If they dropped it to factory recommended from sidewall, it will be a hit of several mpg. Check to make sure that the pressure is equal side to side. I have seen pressures differ by up to 5psi per tire.
     
    #6 msirach, Jan 13, 2010
  7. Joe166

    Joe166 New Member

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    I have never seen a "factory recommended" tire pressure on the sidewall of a tire. How could they do that unless the tires are exclusive to one particular car?

    Door jamb? Yes. Owners manual? Yes.
     
    #7 Joe166, Jan 13, 2010
  8. Senior Chief

    Senior Chief Junior Member

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    Good points all. Thanks for your responses. When looking at the worksheet, I did note that the tire pressure had been checked, and the tech had noted he made it 40psi. Am I correct in saying that 44psi is max.?
    About the 0W-20 vs. 5W-20. Toyota said I had my choice and that both were valid and warranteed. Your right about the new rule on changes at 10K. Had I known it at the time it would have been a no brainer. At the end of my 10K miles I plan on having it serviced with 0W-20 synthetic again. I hope it's the tires (I'll check tonight when they cool down) because I can't figure the slight difference in viscosity would cost me so many mpg's. Thanks. Senior Chief
     
    #8 Senior Chief, Jan 13, 2010
  9. Dark_matter_doesn't

    Dark_matter_doesn't Prius Tinkerer

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    I don't think it's a good idea to run a conventional oil for 10k miles. Did the service dept people explicitly tell you that you could go that long on non-synthetic oil and not void the warranty?
     
    #9 Dark_matter_doesn't, Jan 13, 2010
  10. ksstathead

    ksstathead Active Member

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    Dark is onto something. The extended interval applies only to 0W20, which is a synthetic.
     
    #10 ksstathead, Jan 13, 2010
  11. spiderman

    spiderman wretched

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    Yeah, I second this thought... Get the service guy to put it in witting as it is contrary to the manual. Bet they don't.
     
    #11 spiderman, Jan 13, 2010
  12. Paradox

    Paradox Prius Enthusiast / Moderator
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    So how much was a regular oil change? If kept for say 5,000 miles, it may cost the same to just go with synthetic from the get go.
     
    #12 Paradox, Jan 13, 2010
  13. Senior Chief

    Senior Chief Junior Member

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    Miscommunication. When I said I'd switch when it gets to 10K miles, I meant another 5K with the non-synthetic oil. That would be when the car wil turn over a total of 10K on the odo. If the free coupons come out in Feb. I'll get a free change.
    Senior Chief
     
    #13 Senior Chief, Jan 14, 2010
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