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2004 Toyota 4Runner Question: Isiy ok to mixed transmission Fluid - regular & synthetic



filesmyr, 4.0L V6, Tucson, AZ, May 23, 2010, 18:42

Hi, My Mechanic used four QTs of Coastal DexMerc Auto transmission Fluid and two QTs Coastal Synthetic Blend Mercon V Auto Trans Fluid when he serviced the transmission in my 4Runner 2004 (6 Cyl) SUV. Wll that cause problems to my transmission? I have always heard you should not mix regular with synthetic. Please advice... Thanks

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  • Answer #1

    May 23, 2010, 20:06

    This was not a 'smooth move' by your mechanic. Why did he do this, did he run out of one? I would ask for the correct fluid and all quarts of that fluid ASAP. Synthetic fluid has a different chemistry.
    Most modern vehicle REQUIRE a synthetic ATF, so I would say that your mechanic preformed poorly!
    Most of the literature requires that Toyota factory type IV fluid be used in your truck. When I service a Transmission like this, I ALWAYS use the factory fluid!!
    For example, if you don't use Honda fluid on a Honda, the seals crack and you have to completely OVERHAUL the transmission. I view a Toyota in the same class. If a factory puts out its own trans fluid, they do it for a very good reason, that being, the component requires a special fluid!!

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