20hp Kohler running cooler with 15w-40

Discussion in 'Mechanic and Repair' started by nosparkplugs, Apr 23, 2008.

  1. nosparkplugs

    nosparkplugs LawnSite Gold Member
    Messages: 3,444

    I just changed the oil in the Walker, was already running Amsoil 5w-40, switch to Amsoils 15w-40 heavy duty marine diesel & gasoline 12 tbn oil. What a difference in the operating temperature of the 20hp Kohler air cooled engine. Their is a 150 degree cooler temperature difference in the cylinder head temp, thats confirmed with a lazer temperature gauge after several passes over a zyoshia yard today. When I lifted the hopper up on the Walker, the engine compartment is noticably cooler with the 15w-40 oil. Kohler recommeds a 5w-30 or 10w-30?
  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029


  3. nosparkplugs

    nosparkplugs LawnSite Gold Member
    Messages: 3,444

    Manufacturer's's only recommend their proprietary oil; which is manufactured under their own label buy a unknown oil company. I have yet find out who Kohler has manufacture their proprietary 10w-30 or 5w-30.

    Far to many people are willing to entrust their engines to a 2 year warranty; which under normal wear a Kohler v-twin usually is maintenance free until the 2 year warrenty expires, I speak from previous experience I have blowen one 20hp Kohler; which I used non synthetic 10w-30 in, and followed Kohlers maintenance schedule. When I had the ztr repowered with a new 20hp Kohler, and the blown kohler was dis-asembled for inspection, one conclusion was made: catastrophic engine failure, the high operating temperature, and constant load the engine was under. Unlike an liquid cooled engine, an air cooled engine, has only two ineffective means to cool down, ambient air moving over the cylinder head cooling fins & the oil cooler, and the quality & grade of engine lubrication.

  4. nosparkplugs

    nosparkplugs LawnSite Gold Member
    Messages: 3,444


    Many petroleum products are graded according to the ISO Viscosity Classification System, approved by the international standards organization (ISO). Each ISO viscosity grade number corresponds to the mid-point of a viscosity range expressed in centistokes(cSt) at 40 deg C. For example, a lubricant with an ISO grade of 32 has a viscosity within the range of 28.8-35.2, the midpoint of which is 32.

    Rule of Thumb: The comparable ISO grade of a given product whose viscosity in SUS at 100 deg F is known can be determined by using the following conversion formula:
    SUS @ 100 deg F/5=cSt @ 40 deg C.
  5. mowermankevin

    mowermankevin LawnSite Senior Member
    Messages: 270

    I have always believed that heat transfer is critical to engine longevity,carbon buildup, dirt around cylinder heads,dirty air and oil filters,all that simple stuff,and then came STP, old stuff now, then Teflon and now synthetic oils,I believe what your doing will help extend engine life, and you have the scanner proof, keep on trudging, I can't help but think your on a good track. Please keep us posted, right or wrong,keep a log of what you have done, and the results.
  6. DreamtheGreen

    DreamtheGreen LawnSite Member
    Messages: 145

    Dixie Chopper recommends Lucas 15w-40 long drian truck oil in the Kohler & Generac motors. I use it.
  7. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 964

    "Their is a 150 degree cooler temperature difference in the cylinder head temp, thats confirmed with a lazer temperature...."

    I think you hit the "C" button the meter! Switch it back to "F".
  8. tomo

    tomo LawnSite Senior Member
    Messages: 660

    hello ,
    Temp is always best measured from the sump oil ,particulaly with an air cooled motor .Cylinder head temp can change easily and is not accurate enough and may take many readings to get an accurate indication [to many variables in mowing application] This applies to most engine brands etc . An air cooled engine such as a kohler which ''''IS NOT''' a full industrial engine . [BUILT TO A PRICE ]. There fore finding elevated temps greater than is acceptable can be expected . All aircooled engines dissipate the heat unevenly ,which can result in a typically shorter life than a liquid cooled unit .

  9. nosparkplugs

    nosparkplugs LawnSite Gold Member
    Messages: 3,444

    Air cooling theory is: the majority of the heat & cooling is done at the head where the heat transfer fins are, What engine for the walker do you prefer
  10. tomo

    tomo LawnSite Senior Member
    Messages: 660

    first choice would be a kubota diesel
    second choice would be a gaser kubota [no longer installed in walkers ??]
    third choice would be a kohler gaser

    This is based on engine build quality etc
    To refine this ...
    engine availability etc
    depending on country eg in usa kohler cheaper than kubota
    In oz the replacement engines are the same or very close in price
    Then u come to fuel prices in the usa fuel/gas is cheap, in oz the gas and diesel are similar in price

    On the subject of kohler as a gaser
    The positives r that
    The faults that kohler do have with there engines are well documented and mainly due to kohler engines being used by many machine makers
    The kohler customer servive is also good
    The engines are available in mini block , short mtr , long mtr most other makers do not do these variations

    On a personal note i have suffered most of the common issues with the kohler brand inlet manifold leaking vacumn /poor gasket
    head gasket issues
    coil failure
    the ever present back firing if turned off incorrectly
    fuel pump failure and filling sump with fuel
    hot running leading cylinder when fitted to walker
    the sump oil running very hot
    limited sump oil capacity 2qt [any engine issues can cause the sump oil to be consumed there is no safety margin for this ]
    due to the horizontal shaft arrangement the air inlet screen is low to the ground . The suction from the fan picks up candy bar wrappers etc . If this happens the engine does not cool and a spike in oil temp of 50-80f is common [NOT GOOD] until rectified
    the use of the horizontal arrangement on a hot day with dry grass conditions can cause the the cooling fins to fill up or block easily ,leading to high oil temps


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