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Synthetic oil for a Kohler 20hp ?

Discussion in 'Mechanic and Repair' started by ts923, May 11, 2008.

  1. ts923

    ts923 LawnSite Member
    Messages: 15

    I have a Kohler 20 hp. (M20S) and need to change the oil. This will be it's 11th season of mowing and it has 400 hrs on it. I want to switch over to synthetic oil instead of the regular dino oil but I'm not sure I can. I happened to notice in my owner's manual that Kohler recommends 30W oil. I haven't been able to locate 30W oil that is synthetic in my area and other said I could use 10W30. Can I safely switch my engine to use synthetic 10W30 oil without any issues? Also if I'm able to switch can I increase the change interval of the oil and filter. I currently do it every 25 to 50 hours, and if I can increase it, what would be a safe time frame? I did a search on this forum, but couldn't really find any definitive answers related to my specific question. Thank you.
  2. heritage

    heritage LawnSite Bronze Member
    Messages: 1,356

    Yes you can.

    Use 10-40w Synthetic.

    I go by "Oil Color" when using Syn oil in Gas engine applications.

    When you cannot read the hatch marks on the dipstick....I change it.

    Synthetic is great!

  3. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 963

    By it's nature, synthetic multi weight oil is somewhat "akin" to a straight weight oil.
    Think of water- the viscosity is pretty much the same from 33-211 degrees.
    Amsoil even has an oil rated 10W-30/30.

    I've not seen ANY small engine manf. say you can extend the oil change interval by using synthetic.
    Personally, if I was using the engine in a "commercial" application, I probably would, on an engine out of warranty. Unless I was using it in dusty conditions.
  4. Happy Frog

    Happy Frog LawnSite Bronze Member
    Messages: 1,224

    Dust as nothing to do with oil :nono::laugh:
    Higher oil temperature of air cooled engines is what deteriorate the oil quicker not the dust. Dust clogs the air filter which in returns reduce the available engine power.
    Use Amsoil Formula 4-Stroke® 10W-30/SAE 30 Synthetic Small Engine Oil (ASE) and change at normal intervals on air cooled engines and extended intervals (+ 100% max.) on liquid cooled engines when using Amsoil oil filters.
  5. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 963

    Crankcase breather on a MAGNUM engine!
  6. lawnboy dan

    lawnboy dan LawnSite Gold Member
    Messages: 3,711

    go back and read your manual-shure it dosnt call for 10-30w? no kohler uses 30w that i know of
  7. ts923

    ts923 LawnSite Member
    Messages: 15

    From my manual: (copied and pasted here)
    "Straight 30-weight (Kohler "Magnum") oil is
    preferred. SAE 10W-30 oil is not recommended above
    32°F. Using this oil substantially increases oil
    consumption and combustion chamber deposits."
    That's why I questioned if I could use 10W30 synthetic without any problems as I am operating it at temps above 32 degrees. I didn't know if using synthetic could overcome the issues the manual says can happen if you use 10W30 at temps over 32. Would 5W30 be a better choice, or is it too thin? If I could use 5W30 it might be easier as that's what I use in my vehicles and I can buy all one viscosity at the same time.
    Note: In the past I have used 30W oil in the engine since Day 1 going by what was recommended to me by the dealer I bought it from and the manual itself.
  8. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 963

    And just what models of Kohler engines do you "know of"?
  9. lawnboy dan

    lawnboy dan LawnSite Gold Member
    Messages: 3,711

    i have kohler command in 13 and 23 hp. both say to use only 10-30 oil only.due to the hydro valves
  10. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 963

    Well, this poster has a Kohler Magnum.
    Kohler also has made a K, KT, Triad & Aegis series, along with the current Courage.
    K series probably came out about the same time as multi weight oils.

    The fact that you aren't aware the crankcase breather can ingest dust just shows your ignorance.
    Things were less well "sealed" from the atmosphere on older engines.

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