Hi Scotty, I have a 2004 Toyota Avalon with 143k miles and the transmission fluid has never been changed. It is dark in color and I think I need to change it, but my dad tells me changing the transmission fluid could mess with the transmission and cause it to breakdown. Can you tell me if this is true or not?

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generally that's not the case with toyota. with American cars, yes, don't change em. But those it usually helps