It's Dexron VI (6) not IV (4, never existed as a final product. No such thing as V or 5 either.). It is backward compatible but I recommend you fully replace the old fluid. The viscosity between the two is different and while it's still not well mixed in a power steering system you may notice off and on excessive response or resistance. Also, as it's thinner and will have active detergents, if you have a leak, expect it to be worse.
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