Separate the three negotiations
A vehicle purchase involves the price, the trade-in value and the financing. Negotiating them as one monthly payment makes it easy to give ground on one while appearing to gain on another. Settle the price first, then the trade-in, then compare financing.
Why pre-approval matters
A quote from your own bank or credit union establishes what you can borrow and at what cost. It becomes the benchmark the dealership has to beat, and it removes the pressure to accept the first financing offer presented.
Term length and depreciation
Longer terms reduce the payment and increase total interest. They also extend the period during which the balance exceeds the vehicle's value, because vehicles depreciate fastest early on. A larger down payment and a shorter term both shorten that window.
Add-ons
Extended warranties, protection packages and gap coverage are usually optional and often negotiable. Financing them adds interest to their cost. Price each separately and decline what you do not want.