In a large skillet, heat oil over medium. Add onions; season with salt and pepper. Cook, stirring frequently, until golden brown, 12 to 15 minutes. Let cool to room temperature.
In a medium bowl, combine onions, sour cream, cream cheese, vinegar, and chives; season with salt and pepper. Chill dip until slightly thickened, about 1 hour; or cover and refrigerate up to 2 days. Serve with chips.