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5w30 oil means what????

Discussion in 'Shop - Engine' started by charlie_brown, Aug 7, 2010.

  1. charlie_brown

    charlie_brown Well-Known Member

    Joined:
    Oct 19, 2002
    Location:
    Yorba Linda Ca
    o.k. each week during the summer, I have been giving my daughter a subject that she has to research and write me a one page report on it. I give her some questions that I want her to answer to help guide her. i give her things that i know she will never learn in school.

    This week I gave her one about motor oil. I thought it would be some what simple. After doing a little research my self to confirm what I thought I knew just confused the hell out of me.
    The main part is the weights of the oils and what do they mean. I have heard many things over the years like the 1st number is the weight when you 1st start it up then after warmed up it changes to the higher number. After reading some things I don’t think that’s right.

    Can some engineers help out?
    This is one site I was reading. http://micapeak.com/info/oiled.html
     
  2. burninfuel

    burninfuel Active Member

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    Jun 27, 2009
    Location:
    Fish Springs, Nevada
    5 weight at start up and goes to 30 weight when 200 f or more. 5 weight for easy starts in cold weather and tight clearance engines, modern engines
     
  3. manicmechanic

    manicmechanic Active Member

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    Dec 11, 2005
    Location:
    Washington
  4. charlie_brown

    charlie_brown Well-Known Member

    Joined:
    Oct 19, 2002
    Location:
    Yorba Linda Ca
    Ok let me see if I can get this half right. Basically the first number is the weight of the oil.
    The “W” stands for approved for winter use not weight like most think.
    The 2nd number is where it gets tricky. It is basically a reference number of how much the oil will change as temp goes up. IE: a 5 viscosity oil with the additives added (polymers and others) to make it a dual viscosity type oil (5-15). As the oil heats up, the polymers stretch out and the oil will have a higher rated viscosity. The higher viscosity is rated to the equivalent change of what a 15 weight oil will be.
    So a 5W-15 oil starts out a 5 weight viscosity but when heated, it does not change to a 15 weight viscosity, it changes at the way a 15 weight viscosity oil would change at a designated temp.
    Am I half right??


    from what i have read, this is a crude one liner basic understanding that would be more then the average person knows.
     
  5. jeff

    jeff Super Moderator

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    Apr 1, 2001
    Location:
    California
  6. charlie_brown

    charlie_brown Well-Known Member

    Joined:
    Oct 19, 2002
    Location:
    Yorba Linda Ca
    ^^^ i started to read that but fell asleep after chapter 4. i think i am more confused then a 3 year old. i am going to have to tell my daughter to just make sure she usese the manufactory recommendation and call it a day.

    why cant they make it simple like a 5W-30 where the fist number is viscosity at start up and the 2nd is when it gets hot. oh, wait, i know now, if it was simple, we would not need training classes and have to have degrees or certificates to understand and most any body could get a job working in the field. The more complex they can make it, the more training/certificates/degree one needs to work in that industry which = more money to pay them which cost everyone who wants a bottle of oil more. So lame what and where our country is going. Sorry for the rant.
     
  7. manicmechanic

    manicmechanic Active Member

    Joined:
    Dec 11, 2005
    Location:
    Washington
    Must be the rating game, same reason a 2 ply tire is rated 6 ply. And thanks Charlie, At least I wont call it 5 water 30 anymore.
     
  8. jeff

    jeff Super Moderator

    Joined:
    Apr 1, 2001
    Location:
    California
    Anything can be made difficult with enough effort. ;)

    I think the main thing for your daughter to understand would be the use of an improper oil type can cause increased wear over time. Oil viscosity is based on the oil having a temp of 100* C (210* F). Knowing that in extremely cold or hot climates the need for a lower or higher viscosity oil is necessary would help. Maybe she'll move "North" for school some day. Knowing that the oil in an engine never reaches proper temperature (over cooling, climate, etc) is important. Using an oil with a viscosity closest to "ideal" for that particular engine and operating temp can be better than just going by the oil fill cap. Say she finds herself in Alaska mid-winter and the old Chevy oil fill cap recommends 10w40... she should know enough about oil to recognize the cap is doing her a disservice. And she should know that 20w50 in sub zero temps will barely pour out of the bottle. That should be a hint that the oil is not correct for the climate.

    How about something easier like gear oil, trans fluid, engine oil, and why it's important you don't fill an engine with gear oil and and a rear end with 0w30. Maybe a report on GM's own oil spec Dexos 1 and Dexos 2? Or why you shouldn't mix Orange DexCool with regular Green anti-freeze or tap water?

    Aloha
     
  9. charlie_brown

    charlie_brown Well-Known Member

    Joined:
    Oct 19, 2002
    Location:
    Yorba Linda Ca
    thanks jeff, thats what i will do. we are taking this week off after this oil stuff. next week she will start with tires and what all the number mean, wear marks and so on.
     
  10. glamiskid395

    glamiskid395 Member

    Joined:
    Apr 5, 2008
    Location:
    Moreno Valley, CA
    I actually just learned about oils a couple weeks ago at UTI. what was stated above summed it all up. I never knew what the two numbers meant between hot n cold. I thought that the oil would break down when it got hot and become like 5 weight. My dad thought the same so we always ran straight 30. Now we run 10w-30, but my race truck engine has 200,000 street miles with 30 weight and it never had problems or sludge build up.

    Just think an engine has a cleance of about .003 I think between the bearings and journals. Get a micrometer and try to look thru that gap.
     

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