How much does oil type, grade matter?

Discussion in 'The Garage' started by Breezlife, Sep 15, 2019.

  1. DonM

    DonM Do-dah Do-dah Supporter

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    A1CEBE05-6FED-4C32-913B-E6635B404BED.jpeg
    #61
  2. old scoot

    old scoot Been here awhile

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    I've never seen a single grade [50 wt ] synthetic oil I don't think.
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  3. Plaka

    Plaka Brevis illi vita est

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    The trick is when the warranty is 30 years gone and the formulations of oils are changing rapidly due to regulatory restrictions. Then one needs to know what the machine needs, mostly in the oil formula.

    Oil viscosity has everything to do with flow and pressure. If the oil is two thick the pressure will rise (all else being equal). This can blow coolers, gauges and pressure switches. Too thin and the pump can cavitate, flow suffers along with bearing lubrication. Plain bearings are not lubricated by 'thickness' but by flow. if thickness would do it, they would be packed with extremely high viscosity oil, that is, grease.
    #63
  4. anotherguy

    anotherguy Long timer

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    You've not been paying attention. Available from several manufacturers in various straight viscosities.
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  5. PeterTrocewicz

    PeterTrocewicz Been here awhile

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    You are correct, flow is important. But do not forget that thickness does affect flow. Too thick and the oil will lot flow well enough to provide the lubrication. It is this resistance to flow which causes pressure to rise as well in pressure-lubricated engines. And excessive thickness can also cause cavitation in the pump thereby restricting flow because the pump cannot draw it jn fast enough. And too thin will not provide enough film strength to prevent metal-on-metal contact. Too will can also drop the pressure to the point where the oil cannot do its job. And thickness is affected by temperature, therefore the hotter the climate, and the hotter the engine runs due to design or placement, the thicker the oil needs to be to do its job. Even splash-lubricated engines have a minimum oil thickness recommendation.
    #65
  6. anotherguy

    anotherguy Long timer

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    Viscosity is not as literal as it once was. Look at cSt numbers for various 30 wt engine oil and see the differences. Synthetic oils gave the freedom of engineering traits into fluids.
    #66
  7. PeterTrocewicz

    PeterTrocewicz Been here awhile

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    Thanks for making me do the refresher on cSt. The SAE grade is the classification group or class or range, with a range of thinner to thicker oils within that group. Much like we do with motorcycles: a 1000 class bike can have a motor with an actual displacement of a little less or a little more. The cSt is the actual measurement of the oil viscosity, at least at warmer temps, they use cP at lower temps.
    I do enjoy this kind of research. Thank you again.
    What I did not have to research again is the fact that the engineering freedom from the synthetic oil is provided by the uniformity of the oil molecules that allow it to be used longer and harder due to greater resistance to thinning with temperature and breaking down. So I havwen't killed too many brain cells yet :lol3
    #67
  8. anotherguy

    anotherguy Long timer

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    You're welcome. Yeah me too.
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