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Multi viscosity oil question

Discussion in 'The Hokey Ass Message Board' started by GARY T., May 10, 2012.

  1. GARY T.
    Joined: Mar 23, 2008
    Posts: 1,985

    GARY T.
    from S.W. Pa

    On 2 guys garage on TV they said that 10W30 oil is thin like 10W when cold and heavy like 30WT when hot. I've never heard this before----anyone else???
  2. swifty
    Joined: Dec 25, 2005
    Posts: 1,761


    I think someones got it arse-about, either you or them. 10 when hot and 30 when cold. Can't remember the temps that they measure the viscosity at but if you went to an oil companys website you'd find the info
  3. Bigchuck
    Joined: Oct 23, 2007
    Posts: 1,141

    from Austin, TX

    Always wondered why then does oil drain out of a cold engine like molassas, and gush out like water on a hot engine.
  4. powdercoater46
    Joined: Oct 27, 2009
    Posts: 246


    I thought I knew the answer to this but now your statement makes me wonder who is correct.

  5. wingman9
    Joined: Dec 30, 2009
    Posts: 804

    from left coast

    Gary T is right. Oil is usually tested at 100F and 210F. Here is a quote from Blackstone Labs.

    "The most common grade of automotive oil in use today is the 5W/30, which is a mineral oil refined with VI additives that leave it reading as an SAE 5W viscosity when cold, yet an SAE 30W when hot (210F)."

    The viscosity ratings for synthetic oil work the same.
  6. Special Ed
    Joined: Nov 1, 2007
    Posts: 6,562

    Special Ed

    Multi-grade oil does not physically and literally become "heavier" as it warms, but takes on different (and beneficial) lubricating properties of that of a higher viscosity lubricant.
  7. unkledaddy
    Joined: Jul 21, 2006
    Posts: 2,865


    What have the 2 Guys been smokin'?
  8. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don

    Always wondered why then does oil drain out of a cold engine like molassas, and gush out like water on a hot engine.

    And that is why you should never change oil on a cold engine. The cold oil leaves crap inside, the hot oil carries it out into the drain pan. That is how detergent oil works.
  9. To rephrase what it means; 10w30 has the properties of a 10 weight oil when cold, and the properties of a 30wt when hot. It doesn't get thicker, it just doesn't thin as much. It acts like a 30weight oil does at that temperature.

  10. belair
    Joined: Jul 10, 2006
    Posts: 8,649


    But how does it KNOW????
  11. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,955

    gas pumper

    Detergent oil keeps the stuff in suspension. That's why in the days of non-detergent oil the instruction was to drain hot while all the stuff is still floating in the oil.

    And there still was always a layer of crap in the pans when you took one apart.
  12. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,955

    gas pumper

    I just watched the Modern Marvels show "OIL" They explain this. It's some kind of chemical magic.
  13. its friggin magic!
  14. Because the engine is cold. Even a 10 viscosity will be thicker at 60 degrees. But a 10 viscosity will flow better than a 30 viscosity at the same 60 degrees; the 30 viscosity will be thicker.
  15. The way I'd heard it explained for say 10w30 oil is that when it's cold, it's no heavier than a straight 10w at that same cold temperature.

    When it's hot, it's no thinner than a straight 30w oil at the same high temperature.

    That sounds right, doesn't it? :confused: Makes sense to me at least, for what that's worth. :rolleyes:
  16. bohica2xo
    Joined: Mar 6, 2012
    Posts: 153

    from Las Vegas

    Viscosity. Very misunderstood.

    Oils all thin out as they get warm. NONE of them get thicker. A single grade oil is just thicker when cold than a multi grade oil. Oils are graded at two temperatures. 40c & 100c . The measurements are taken in centistokes, abbreviated cSt Now, let's look at some common oils:

    At 40c or 104f first:

    5W30 47 -52 cSt
    5W40 85 - 89 cSt
    15W40 102 - 108 cSt
    20W50 129 - 166 cSt
    30W 98 - 110 cSt
    40W 130-150 cSt

    A pretty big spread right? Now remember, the higher the number, the harder your oil pump works to move that stuff around. And those numbers go up more as the temperature drops.

    Now let's look at 100c or 212f :

    5W30 10 -12 cSt
    5W40 13.50 - 15.5 cSt
    15W40 14 - 16 cSt
    20W50 16.5 - 20 cSt
    30W 11.5 - 12.5 cst
    40W 14.5 - 15.5 cSt

    Much thinner at operating temps. a 5W30 oil is still as "thick" at 100c as your straight 30. But on a cold morning it puts 1/3 the stress on the oil pump drive, and is more likely to splash where it needs to be during cranking.

  17. Tom S. in Tn.
    Joined: Jan 16, 2011
    Posts: 1,108

    Tom S. in Tn.

    This is the way it was explained to me below, but thanks bohica2 for posting this above ^^^^. Now I understand it. Tom S. in Tn.

  18. greaseguns
    Joined: Dec 24, 2006
    Posts: 135


    my flatty has better oil psi hot with 30w than if i use 10w30 ? whats up with that
  19. Relic Stew
    Joined: Apr 17, 2005
    Posts: 1,130

    Relic Stew
    from Wisconsin

    They start with a straight oil and add chemicals to it. For 10W30, they start with 10 weight and add chemicals that flow smoothly when cold, but as they get hot, start to cling and tangle together, slowing down the flow of the hot oil. 10W40 has more chemicals and less base oil than 10W30.
  20. Road Runner
    Joined: Feb 7, 2007
    Posts: 1,257

    Road Runner

    It's the polymers added to multi-grade oil that do the 'magic'.

    They 'curl up' when cold and 'stretch' when hot.

    The first number in multi-grade oils is the base oil viscosity, the second is how the oil behaves at 100 degrees Celsius (or 212 F).

    So 10W-30 is basically a straight grade SAE 10W (W=winter) that will start in cold temps like the 10W it is, but as it gets warmer and the polymers stretch, it acts like the thicker straight grade SAE 30 that flows slower.

    Seems like the perfect oil to use, but the added polymers break down over time from shearing action and stop being effective as the oil gradually acts more like the base oil it is.

    Make sure to change the oil before that happens, after about 3-5K miles.

    Another argument against multi-grade oil is that straight grade oil lubes better than oil with polymers that make up a large part of the overall additive package.
  21. Ain't it a bitch when a can of oil is smarter than some of us?

  22. rbonazzoli
    Joined: Feb 16, 2012
    Posts: 141

    from Dallas, TX

    On a related note, today's oil, no matter the viscocity, is not designed to protect non-roller camshafts. Because of the need for emissions systems to be warranteed for 10 years, ZDDP has been phased out of conventional motor oil for years now. Although I have not had a cam lobe wiped out, I have read enough on the topic to believe it is a real concern. I now add a bottle of ZDDP (available from Summit) during each oil change.
  23. mustang6147
    Joined: Feb 26, 2010
    Posts: 1,847

    from Kent, Ohio

    What 2 guys said was, 10w30 is 30 weight oil that acts like 10.... and 10 that has the same characteristics as 30..... Its the reason multi viscosity came out...

    Same principle when it comes to hydraulic lifters.... If they where solid you would have to adjust them all the time..... Oil would have to be changed almost monthly cuz of temp change..... Multi viscosity gives you a broader range for operation....
  24. BigPerm365
    Joined: Jan 8, 2012
    Posts: 47


    There is a very infomative article written by some RedlIne Oil engineers, ( not a commercial ). Look around on the internet for " More than you ever wanted to know about Oil"...& it'll explain.
  25. George
    Joined: Jan 1, 2005
    Posts: 7,388


    And apparently where true racing oil used for racing is changed frequently the additive package is designed to be used up(dead) by 1,000-1,500 miles @ the most.
  26. JEM
    Joined: Feb 6, 2007
    Posts: 1,040


    Are you using modern API 'Energy Conserving' 10W-30?

    The API oil viscosities are a RANGE, and the typical late-model 'Energy Conserving' oil is formulated to be at the thin end of that range.

    A 10W-30 (0W-30, 5W-30, 5W-40, whatever) that's got the German-mfr scrambled eggs on it (BMW LL01, MB 229.2, VAG 502.00) will NOT have 'Energy Conserving' in the little API circle and is a considerably thicker oil, not to mention having been specifically tested for high-temperature shear-stability (American and Japanese mfrs like thin oil for fuel economy and they'll take small oil capacity and relatively short change intervals; the Germans want 12-18K-mile change intervals so they have 7-10qt oil capacities, big filters, and stringent oil specs.)

    It doesn't fix the lack of extreme-pressure additives in the SL/SM/etc. oils, though. The standard-issue modern motor oils are not made for engines with sliding things in them. Even the diesel oils have gone API SM now.
  27. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,480

    Rusty O'Toole

    When 10W30 is cold, it is as thin as cold 10W

    When it is hot, it is as thick as hot 30

    In other words it thins out but not as much as straight 10W.
  28. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,480

    Rusty O'Toole

    Because it is magic.

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