Synthetic vs. Multi-Purpose Fluids - NOT OIL QUESTION

Discussion in 'KK General Discussion' started by JeepLibertyKK, Mar 27, 2020.

  1. JeepLibertyKK

    JeepLibertyKK New Member

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    Dec 1, 2013
    Rohnert Park
    I'v been dragging my feet getting all the necessary fluids for some maintenance work on my 2012 Jeep KK and 2003 Suburban, both four-wheel drives. Some of the fluids match up viscosity-wise, but not necessarily fluid type. For example, the older Suburban recommends 'synthetic' products for the front and rear axles but the Liberty states 'SAE 75W-90 Gear Lubricant' and 'SAE 80W-90 Multi-Purpose API GL-5 Gear Lubricant' as opposed to 'SAE 80W-90 Synthetic Axle Lubricant' for the Suburban.

    I've always assumed that in these types of applications, synthetic is acceptable. But I don't want to assume and then do long-term damage to any Liberty components.

    Your experience and recommendations would be appreciated!

    Thank you.
  2. LibertyTC

    LibertyTC Well-Known Member Staff Member Moderator

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    Oct 24, 2008
    B.C. Canada
    Always refer to the owners manual for your 2012 KK under specifications. Go with what is recommended.
    As an example the rear diff may stipulate DINO 75W-90 but there may be clauses regarding if towing, where a thicker gear lube is required.
    Also note what the change frequency is, on the KJ it is every 20K miles for rear diff.
    I prefer the Lucas Dino gear lube wherever possible.
  3. tommudd

    tommudd Moderator Staff Member Moderator

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    Jul 14, 2005
    Southeastern Ohio
    ONLY reason they went to synthetic was to try and get that 1/10 more MPG, pure and simple
    On gears in your diffs you want something that will " cling " to them so good old dino is the best period
    I run 85-90/140 in all 3 of my Libertys all the time, of course they all pull trailers, 2 of them are used out in the fields etc on the farm so all get used
    Plus I run them , wife works 5.5 hours away so nothing to jump in one and take off to see her for the weekend so I want something I can trust