Mobil 1 20W50 engine oil in Kohler Magnum Engines Experiences

Discussion in 'Mechanic and Repair' started by Gravely76, May 14, 2009.

  1. Gravely76

    Gravely76 LawnSite Member
    Messages: 33

    I am interested in learning what experience(s) you have had with Mobil 1 20W-50 fully synthetic in Kohler Magnum 20 engines.

    Thank you
  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Can't help on this one, I only use the factory recommended weight oil in everything.

  3. tomo

    tomo LawnSite Senior Member
    Messages: 660

    Hi ,
    The use of 20/50 oil
    I have only used /tried 20/50 once and that was a mineral grade in a kohler
    The results are very similar as if u were to use it in an auto engine

    Although the engine may be able to deal with the oil when it is hot it is the start up that is the issue

    cold start
    it is difficult to pump particularly for a small engine that has a small oil pump as well . The kohler oil pump is very small . Most engine wear occurs during start up , The oil pressure light was still on 1-2 seconds after start up at its worst .

    running temp
    a 50 weight oil at operating temp causes a little to much drag on engine components for me . oil pressure should be good 40lbs and above

    summary for warm ambient conditions [nice day ]
    10/30 to light

    10/40 or 15/40 ideal

    20/50 to thick

    A synthetic may be ok compared to mineral as the start up flow may be better and generally is but the weight of 20/50 does really have no place in a small engine

    A kohler eg 25 hp has a plastic oil pump gear from memory 20/50 = to much load . Remember a kohler is a underdesigned engine [weak] By no means an industrial work horse in reality

    Use use the correct grade [recommended by engine maker] or better eg API SG, SH etc and the viscosity appropiate for the weather conditions

    10/40 typically available in semi syn or full synthetic
    Donot use this oil in a mineral as the additive packages could not handle the 30 w split between 10---40 . This oil did gain a bad reputation 20 years ago BUT with the synthetic oil develop ment it apparently is all good ...
    Having a 30w split or greater is now common

  4. Greenwrench

    Greenwrench LawnSite Member
    Messages: 32

    Semi synthetic oils are but the latest in scams. Oil is only as good as its weakest component. Either go full synthetic or not at all. 20w50 synthetic is just fine for any engine; though the cost is much higher. I recommend 30 weight conventional for air cooled, changed according to manufacturer's intervals, but just about anything is fine if intervals are followed. If you run your mowers when the temperature is 30 F or below, first ask yourself what you are doing mowing in that weather, then shut the machine down and enjoy the time off. If you must run equipment sub freezing, use any synthetic engine oil, or an appropriate rated conventional oil for the expected max low temp. The "size" of the oil pump is irrelevant. Small oil pumps produce as much pressure as big ones: Sometimes even more. Just follow the change intervals with the recommended oil and you will be fine.
  5. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Messages: 2,247

    Restro is correct. Stay with the manufacturer's recomendations.

    I have a Grasshopper 1822K that I bought new in 1987 and it has seen a steady diet of Valvoline 30W HD since new and is changed every 50 +\- hours. Engine runs like new and absolutely no oil consumption. Regular service is the big KEY-oil, oil filter, air filter, fuel filter.

  6. Triple L

    Triple L LawnSite Senior Member
    Messages: 514

    I've ran 20-50 synthetic in my walker with an 18hp Kohler since day 1... Over 2400 hrs been flawless so far... Still runs just as good as it did on day 1
  7. tomo

    tomo LawnSite Senior Member
    Messages: 660

    Hi ,
    The oil pump gear when made out of plastic or similar have an increased potential for excessive wear and failure

    Using to thicker oil is the same as using a larger oil pump . Increased oil temp and the likelyhood the pressure releif valve will operate at startup . The delay in oil flow at start up will cause wear over time .This is particularly an issue if the engine has a large oil cooler setup .The concept of flow needs to be understood ..

    Mono grade oil is well proven not to protect as well as a multigrade .Eg comparison between 10/40 and mono 30. If people are concerned about 10/40 or a 15/40 being a little thick ,the vicosity will slightly reduce over time


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