Oil Change -- Hot or Cold engine -- or does it matter?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by cyberpriusII, Nov 29, 2016.

  1. cyberpriusII

    cyberpriusII Prodigyplace says I'm Super Kris

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    I actually googled this and found lots of stuff -- mostly on Bob is the Oil Guy....

    But, wanted to see what the opinion was here -- where I somewhat know who is whacko and who is not. :)

    So, changed oil this weekend, but since it was raining pretty good, did not really want to get under the Prius with all the muddy water dripping off and into my face, arms, etc.

    But, having had the point that oil needs to be changed while hot or warm told to me many times by my father, I grumbled and went ahead and it did while hot.

    But, logically, I can't see any real difference if you let it drain for a long while, which I do especially since I use the Fumoto Valve. And, with the new "thinner oil" (5W-30) vs. the straight 30W that my dad used to used, I really think that there should be no real difference.

    On BITOG site, it seemed like it was two-thirds drain while hot and one-third, it made no difference. Any thoughts here. Of course, to avoid the dripping mud water, I could just let it idle in the driveway and warm up without driving, but, that makes me uncomfortable in terms of wasting gasoline, etc for no reason. Plus, I know, stupid, but I am leery of just leaving the Prius idle, vs. other conventional engine cars.
    kris
     
    #1 cyberpriusII, Nov 29, 2016
  2. edthefox5

    edthefox5 Senior Member

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    If the car has sat for a few hours then all of the oil is in the oil pan. Changing hot oil hurts.
     
    #2 edthefox5, Nov 29, 2016
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    I've heard the same advice, and heed it: typically change the oil after coming home with the groceries, or a run to the dealership for supplies. It flows better, and more importantly I think: is homogenized, any sludge/crud more likely to flow out in the drain. And a long drain doesn't hurt, get it draining, then go in for supper or tea.
     
    #3 Mendel Leisk, Nov 29, 2016
  4. edthefox5

    edthefox5 Senior Member

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    Never ever seen crud or sludge come out of any oil pan I owned. If you have to warm up the oil to get sludge out you have more problems
    than the oil being warm or not.
     
    #4 edthefox5, Nov 29, 2016
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you do not have to start the car to get it into position for the oil change, then I would say that changing the oil with the engine cold is fine. The worst case is that a slight film of oil in the crankcase won't drain out because it is cold and therefore thicker than if hot.

    If you have to start the engine to get the car in position then the cold oil will be deposited up into the valve train area, etc. In that case the oil change will not be as complete compared to the scenario where the oil is hot.

    The standard for draining "a long while" is that there should be no more than one drop of oil coming out of the drain hole, per minute. Personally, I find that to be excessive so I don't wait for the drips to decline to that rate.
     
    #5 Patrick Wong, Nov 29, 2016
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  6. bisco

    bisco cookie crumbler

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    the oil should be exactly 87 degrees before draining. if at any point during the process, it drops to 86 or lower, pour it all back in and start over.
     
    #6 bisco, Nov 29, 2016
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  7. William Redoubt

    William Redoubt Senior Member

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    Agreed, with a caveat. If it's over 90 degrees, you have to start over, as well. And send me $5. Them's the rules. Follow them carefully to avoid disappointment.
     
    #7 William Redoubt, Nov 29, 2016
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  8. Mendel Leisk

    Mendel Leisk Senior Member

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    Well, I occasionally need to drive somewhere, so what the heck: I'll change immediately upon getting home. Same story when my kids come over with their cars: roll it in and start draining.
     
    #8 Mendel Leisk, Nov 29, 2016
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  9. edthefox5

    edthefox5 Senior Member

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    The same goes for muffins.
     
    #9 edthefox5, Nov 30, 2016
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  10. Mendel Leisk

    Mendel Leisk Senior Member

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    And color slide processing, very stressful.
     
    #10 Mendel Leisk, Nov 30, 2016
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