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30 or 40 weight oil?

Discussion in 'Mechanic and Repair' started by Vibe Ray, Aug 9, 2001.

  1. JLC

    JLC LawnSite Senior Member
    from IA
    Posts: 467

    I'm running Mobil 1 synthetic 0w30 in my 25 horse Kohler. According to SDWally this would be a good oil I suppose. It is thin at startup to give quick lubrication and has the viscosity of the standard 30 weight when warmed up. Additionally it is sythetic so it won't break down if it gets heated when you are really working the engine. Is this right?
  2. Sammy

    Sammy LawnSite Bronze Member
    Posts: 1,734

    I think that the 15w40 is better than the 10w40.

    The 10w40 needs more/larger plastic to work.

    Fish, Are you the same Fish from the Garden Web Board ?
  3. Fish

    Fish LawnSite Member
    Posts: 139

    Yea, they were getting tired of me over there. I still pop in to
    piss someone off, but Eric invited me, so I thought I would come
    over here and start trouble.
    For some reason the compound of 10w40 is real bad for
    breakdown, I have read reports that all realize this. I always
    recommend straight 30w unless there is a reason, I even run
    it in my van. I have just seen too many engines desroyed by it
    or I would not bother posting. Failures caused by this are
    usually misdiagnosed, and since many engine manufacturers
    used to recommend this oil, they will not be too forthcoming
    to condemn this oil. But type motor oil, oil, or whatever into
    a search engine and you can read reports on oil. You will find a
    small reference to multi-viscosity breakdown particularly with
  4. John DiMartino

    John DiMartino LawnSite Silver Member
    Posts: 2,555

    SAE 30 is the one to use,down to 32 degrees in air cooled motors.Below that,go to a 10w30,or 15w40 diesel oil.15w40 is good stufff,and pretty much can be used year round down to zero degrees,but I like to go thinner below 20 degrees.
  5. Vibe Ray

    Vibe Ray LawnSite Senior Member
    Posts: 785

    Seriously though guys, is there a synthetic straight weight 30 or even 40 out there? All I see is 10W-30 in Mobil 1. And if the SAE 40 is thicker wouldn't that provide better protection? So why go with the SAE 30?
  6. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Posts: 1,712

    Mobil makes more than the X/30W in Mobil 1. A friend uses a 15/40 or probably 20/50 in a hot 454 in a speed boat. Might even make a series 3 for diesel.

    The Rotella oil is a very high quality oil.

    Years ago I switched to oil and grease from TRC - Texas Refinery Corporation. Everything lasted longer. Especially bearings and bushings with the #2 chassis grease.

    I now buy equivalent product thru King Oil, Hagerstown Maryland. Both product lines are expensive but worth it.

    Another friend sells Husquavarna racing bikes. On regular oil they require rebuild after every race and the bearings show wear. On Mobil 1 they go 2 races and they look like new upon tear down. They still rebuild after 2 races because they don't know how far they can really go.
  7. www

    www Guest
    Posts: 0

    All air cooled engines will run better, last longer and produce more power with synthetic oil. B&S (and ALL others) highly recommend the use of either 5W-30 or 10W-30 synthetic oil for all temperature ranges. NO OTHER OIL IS AS GOOD! Also, don't worry about "break-in" with dino oil. You can put synthetic in on the first start of the engine. The engine parts will mate just as well with synthetic as dino (probably better). There is only one thing about dino oil that is better...it's cheaper!
  8. Keith

    Keith LawnSite Gold Member
    Posts: 3,977

    Yes, Amsoil makes a SAE 30. I ran it in my gas Kubota for over 2000 hours. I switched to 10w-30 Mobil 1 because I could only get deals buying 4 gallons at a time. At that point we weren't using it that much.


  9. Wangel

    Wangel LawnSite Member
    from Kansas
    Posts: 54

    Hey fish, what compound are you speaking of in 10w40 oil?

    Remember the car manufacturers used 10w40 for about 20 years in cars without any problems, then shifting to 10w30, and now 5w30. The manufacturers engineers we should all agree would know the best oil for our engines.

    For example: The new Honda tractors actually recommend 10w30 or 10w40 depending on the temperature. Whereas Tecumpseh states specifically DO NOT USE 10w40 oil. So which is it?

    The best recommendation anyone can give is to read the manual that comes with your equipment and to follow it explicitly. Do not follow myths, wifestales, or statesments that start, "someone told me once". Otherwise YOU could be responsible for voiding someone warranty.
  10. Fish

    Fish LawnSite Member
    Posts: 139

    I know oil is a hot topic among people. I typed in motor oil in
    msn search engine and came up with this wives tale right off.
    I can find other articles referring to multi-viscosity breakdown
    if you wish, but I have seen many engines destroyed by it.
    Look at paragraph 7 for the first reference.

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