Preheat the oven to 250°F (120°C).
In a microwave-safe bowl, combine the popcorn oil and ranch dip mix; stir until blended.
Heat the oil and ranch mixture in the microwave for about 2 minutes, then stir and set aside.
Place the Wheat Chex, Bugles, Goldfish, Cheez-Its, and oyster crackers in a very large mixing bowl or roasting pan and stir to combine evenly.
Drizzle the warmed oil and ranch mixture over the combined snacks and stir thoroughly until the mix is evenly coated.
Spread the coated mix in an even layer across baking sheets (use more than one sheet if needed) and bake for 1 hour, stirring every 15 minutes to ensure even crisping.
Remove the baking sheets from the oven, spread the snack mix onto wax paper to cool completely, then transfer to airtight containers for storage.