Even though olives are biologically a fruit, the oil is called a vegetable oil. The use of 'vegetable' to describe oils is primarily to communicate to the buyer that there are no animal products in the oil.
The term "vegetable oil" is generic--it encompasses all oils derived from plant sources, including olive oil. However, products labeled "vegetable oil" for cooking are typically blends containing...
You can substitute vegetable oil for olive oil but.... with veg oil you won't get the desired taste you may be looking for such as salad dressing or garlic and peppers with bread. also veg. oil will...