To know when or when not to use an ingredient, it’s important to know what an ingredient is and what that ingredient does. To begin, both oil and butter are fats which enhance flavor and help dictate the texture of what’s being cooked.
The main differentiating factor between oils and butter is that butter is saturated fat, whereas most oils are unsaturated fats. Another important difference is that oil stays liquid at room temperature, and this quality helps achieve a satisfying moist texture for baked goods.
Butter, on the other hand, stays solid at room temperature, and in contrast to oil, butter has components other than fat that comprise it. About 16% of butter is made up of water, which helps for a sturdier and denser baked good.
It’s important to consider what kind of texture and taste you want to achieve when choosing your ingredients. As mentioned, butter can help achieve a sturdier bake, while different kinds of oils provide a bake that’s more moist, and flavored oils like citrus oil can go a long way for enhancing flavors!