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Can using "B" cause an increase in oil consumption?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Wolfie52, Dec 17, 2015.

  1. Wolfie52

    Wolfie52 Senior "Jr" Member

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    I have a 2004, with about 119,000 miles. It have changed oil regularly and the PCV valve was replaced about 4 months ago. In doing occasional oil level checks I have never found the oil level low, no matter how long since the last oil change. In fact, often it seemed overfilled.

    Recently I drove into the mountains, and used the "B" (engine braking) far more than I have ever used it. Then, when I checked the oil level, after only about 1500 miles since the last oil change, it was down maybe a 1/2 quart. Not below the "low" level but still low.

    It kind of worried me, since I had never seen this before. Has anyone else experienced this after extensive "B" usage? Any guidance appreciated.
     
  2. bisco

    bisco cookie crumbler

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    this is a great question! i'll be interested in the responses. all the best!(y)
     
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Since the use of "B" requires the gasoline engine to spin faster than otherwise would be required, it would not surprise me if engine oil consumption was accelerated.
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Doesn't B create high vacuum too, sucks oil up into combustion chamber?
     
  5. CR94

    CR94 Senior Member

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    It might, depending on what the programming does with throttle position (and possibly valve timing?) while the engine is being spun in "B". One could tell by looking at MAP (manifold absolute pressure) with a ScanGauge while descending a big hill in "B". (Low pressure = "high vacuum.")

    In a more conventional vehicle, in which releasing the accelerator closes the throttle, coasting downhill with the wheels spinning the engine and accelerator released definitely results in high manifold vacuum that can increase oil consumption by a leaky engine.
     
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  6. valde3

    valde3 Senior Member

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    Using B will cause engine to revs and create high vacuum. That’s only way it can create engine braking. Valve timing could be used to limit the vacuum but it would also limit the engine braking. High revs and high vacuum will always cause oil usage. If your engine is worn it can use lots of oil while doing this. But it won’t create much wear so as long as you keep the oil level up it really doesn’t matter.

    And besides you really have no other option. Not using B will cause more wear on HV-battery, brakes, and even brake failure and accident.
     
  7. Ozark Man

    Ozark Man Member

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    I use "B" often but not for a long period of time and have not encountered that problem.
     
  8. Wolfie52

    Wolfie52 Senior "Jr" Member

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    Thanks for your thoughts.
     
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    I'll check ours and report. Got coerced up a local ski hill, Christmas Eve, and was using B pretty much all the way down. Oil was on top mark, will check.