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Motor Oil Basics

Discussion in '80-Series Tech' started by SteveLCetc, Feb 8, 2004.

  1. SteveLCetc

    SteveLCetc

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    After starting to read through the "Synthetic Oil" thread, I realized that was a chore I didn't have time for. There were some misconceptions that needed clearing up though.

    5W-30: This means the oil behaves like 5 weight when cold (40 deg C, or 104 deg F) and 30 weight when hot (100 deg C, or 212 deg F).

    You can visualize this comparison with a couple of funnels - a wide one for cold and a nrrow one for hot. The number is how long it takes for the oil to flow through the funnel. 5w-30 takes e.g. 5 seconds thorough the wide funnel when cold, and 30 seconds through the narrow one when hot. A straight 30 weight takes 30 seconds through both.

    When it's hot, the engine doesn't know the difference between 5w-30, 10w-30, or even straight 30 weight.

    When it's cold, a 5w-30 will flow faster to where it needs to be when you first crank it up.

    Steve
     
  2. IdahoDoug

    IdahoDoug

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    I'd think a better analogy would be to keep the funnel the same size, and it takes longer to get through it when hot. That makes it easy to visualize that it's thicker when hot, eh?

    DougM
     
  3. SteveLCetc

    SteveLCetc

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    Actually it's thinner when hot.
     
  4. IdahoDoug

    IdahoDoug

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    Hmm. I thought the nomenclature of a 5w30 meant: Behaves like a thin 5wt oil when cold, and behaves like a thicker 30w when hot.

    DougM
     
  5. SteveLCetc

    SteveLCetc

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    That's correct, compared to a standardized oil. A 5w-30 behaves like a 5 weight when a 5 weight is cold, and a 30 weight when a 30 weight is hot.

    I'm not sure about a 5w-30, but a 10w-30 is still thicker when cold.
     
  6. Pitbull

    Pitbull

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    [quote author=SteveLCetc link=board=2;threadid=11204;start=msg101416#msg101416 date=1076261687]
    After starting to read through the "Synthetic Oil" thread, I realized that was a chore I didn't have time for. There were some misconceptions that needed clearing up though.

    5W-30: This means the oil behaves like 5 weight when cold (40 deg C, or 104 deg F) and 30 weight when hot (100 deg C, or 212 deg F).

    You can visualize this comparison with a couple of funnels - a wide one for cold and a nrrow one for hot. The number is how long it takes for the oil to flow through the funnel. 5w-30 takes e.g. 5 seconds thorough the wide funnel when cold, and 30 seconds through the narrow one when hot. A straight 30 weight takes 30 seconds through both.

    When it's hot, the engine doesn't know the difference between 5w-30, 10w-30, or even straight 30 weight.

    When it's cold, a 5w-30 will flow faster to where it needs to be when you first crank it up.

    Steve
    [/quote]

    Steve good information, and great description. I'm staying with my Mobil 1 5w30 since it does not buy me anything to switch to a 10w30 in the summer. If anything I might try a 5w40 for year round use if Mobil 1 has it available in my area.

    Thanks
     
  7. Smiddywastaken

    Smiddywastaken

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    Oils

    Ive been using 20w-50 since I have owned my car. Originally when I got it I lived in a high altitude desert where I probably needed it. now im at 55 feet in sunny California. I was thinkin about droppin to a 15w-40? Any input? which Brand does everyone recommend?
     
  8. Tyler93

    Tyler93

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    Chevron Delo 15-40 if your into dinosaurs