I would recommend negotiating the purchase separately and waiting until the end to indicate you'd like to trade your old one in if you don't want to hassle with selling it privately. You're giving up too much info ahead of time that they'll use to finagle the numbers in their favor. If they ask, just say you're considering selling it privately. Sounds like you've already started the process with a dealer and it may be too late to approach it this way. If you decide to shop around, consider using this tactic moving forward.

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