10w30, 10w40, 20w50, 5w30 - what is the difference?

Discussion in 'Off Topic' started by SagaLore, Mar 11, 2004.

  1. SagaLore

    SagaLore Elite Member

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    What do all the different oil weights do, what is good for what? I'm assuming that 10w40 is heavier than 10w30. Right now I have 30 in my car, but the rings are wearing out and I'm losing performance and fuel efficiency - if I put 40 in, can I gain some of that back?
     
  2. Aharami

    Aharami Lifer

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    and whats a 0w40?
     
  3. Analog

    Analog Lifer

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    There should be a lot of links on this out there. Be careful with heavier oil, as it can affect engine wear at start-up and may be affected by the temperatures you're driving in.
     
  4. Analog

    Analog Lifer

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    dbl post.
     
  5. Guest

    The first number is its cold start viscosity. The higher the number, the thicker the oil. In really cold climates, 0w-something is good since it's easier to get oil flowing during cold starts. But for most climates 5w-something is just fine.

    The second number is the oil's viscosity when it's heated up. For most cars, something-w30 is fine, since it provides adequate protection in most situations.

    A good guideline to go by is what's on your car's oil cap says. Mine says 5w30, so that's what I use.
     
  6. SagaLore

    SagaLore Elite Member

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    good information on engine oil

    W = winter.

    So if I'm having a problem with cold starts, but I'm losing compression because my seals are worn out, and I drive long distances at a time - I guess 5w40 would be good for my car?
     
  7. Ameesh

    Ameesh Lifer

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    thanks! ive always wondered what those numbers were for, the oil change place puts 5w20 in my suv
     
  8. OS

    OS Lifer

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    thats what they say but it's kind of counterintuitive that oil gets thicker as it gets hotter.

     
  9. SagaLore

    SagaLore Elite Member

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    Right, the oil gets thinner. I think oil is actually a combination of two different oils, the 10W is the viscosity of the first oil at cold temp, and the 40 is the viscosity of the 2nd oil while it's hot.
     
  10. etech

    etech Lifer

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    No, a band-aid is not the right approach. Fix the seals.
     
  11. mugs

    mugs Lifer

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    Do you own a late model Ford or Honda? I hate that they use 5W-20, it's hard to find synthetic 5W-20 around here.
     
  12. mugs

    mugs Lifer

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    It's actually just one kind of oil with polymers or something like that. It doesn't get "thicker" when it gets hot, it has the viscosity that the thicker oil (40 weight) WOULD have at that temperature, as opposed to the viscosity that a 10 weight oil would have at high temperatures.
     
  13. Vette73

    Vette73 Lifer

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    Don't use 5W20 it is aq gimmick that Honda and ford came up with to save money on fees the goverment charges for gas milage per car.

    Use Mobil1 5W30 or 10W30 year round and you will be ok
     
  14. Evadman

    Evadman Administrator Emeritus<br>Elite Member

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    Oils of today are called "multi-viscosity". A 10w-30 oil has the flow characteristics of a 10 weight when cold (so lube can be rushed to where it needs to go) but a 30 weight when at operating tempeature.

    Oil DOES NOT get thicker as it warms up. It gets thinner. The viscosity diferential is less from hot to cold with a 10w-30 then with a straight 30 weight. It still gets thinner.
     
  15. KGB1

    KGB1 Platinum Member

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    It is rather odd, GM recommends to use 5w30 on my 01 Astro (4.3L V6), while my dad's old 95 bonneville used 10w30(3.8L v6)

    I guess it depends also on how new the engine is, I thought it was based on engine size (cc) in the past, but i see now it has nothing to do with it anymore.
     
  16. moonshinemadness

    moonshinemadness Platinum Member

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    My car has always been run on tractor oil (No idea what viscosity) because i get it free, could this be harming the engine?