Short Answer:

You do not need to add oil to frozen fries when cooking them in an air fryer, as they can crisp up using the hot air circulation alone. However, a light spray of oil can enhance browning and make the fries extra crispy.

Adding a small amount of oil is optional and depends on your preference for texture and taste. Even without oil, frozen fries cook quickly, stay golden, and have a satisfying crunchy exterior with a soft interior.

Detailed Explanation:

Adding Oil to Frozen Fries

Optional Nature of Oil
Air fryers are designed to cook food using hot air, which crisps frozen fries without needing extra oil. The circulating heat evaporates moisture and browns the exterior naturally, creating a fried-like texture. Therefore, oil is not strictly necessary for cooking frozen fries successfully.

Benefits of Light Oil Spray
Using a light spray of oil can improve the appearance, flavor, and crispiness of the fries. Oil helps the surface brown more evenly and creates a slightly richer taste. It is especially useful for thicker fries or breaded varieties, which may benefit from enhanced browning.

How Much Oil to Use
Only a very small amount is needed, typically 1–2 teaspoons for a standard basket of frozen fries. Excess oil is unnecessary because air fryers already provide a crispy exterior through hot air circulation. Too much oil can make fries greasy and reduce crispiness.

Even Cooking Without Oil
When cooking without oil, arrange the fries in a single layer and avoid overcrowding. Proper spacing ensures hot air circulates evenly around all fries. Shaking or flipping halfway through cooking also helps achieve uniform crispiness, even without oil.

Health Considerations
Skipping oil makes frozen fries lower in fat and calories, which is a healthier option compared to traditional deep-fried fries. Using minimal oil maintains this health benefit while still producing golden, crispy fries.

Conclusion:

Adding oil to frozen fries is optional when using an air fryer. Fries can cook evenly and become crispy using hot air alone. A light spray of oil may enhance browning and texture, but it is not necessary. Proper arrangement, shaking, and cooking time are more important for achieving tasty, golden, and crispy fries.