Substituting vegetable oil for canola oil
Short answer is yes, you can almost always substitute vegetable oil and canola oil for each other.
Vegetable oil is made predominantly from soybean oil but it usually is a blend of oils from vegetables such as corn, olive, pumpkin seed, grape seed or even canola oil itself.
Canola oil is made from pressing a plant that is a hybrid of the rapeseed plant. It has the lowest levels of saturated fats out of all the vegetable oils.
Yes you can. You can actually use any oil at all, just be aware that each oil has its own taste and thus the final product will have a slightly different flavor.
But vegetable oil and canola oil are neutral flavored; I doubt anyone is going to notice a difference between the two.
@Jefromi except that veggie oils are much more likely to carry a flavor than canola is. If she was subbing the other way around, I definitely wouldn't worry about it.
@sarge_smith No, not really. Anything sold as "vegetable oil" is going to be neutral (and it'll probably be soybean, or might even be canola anyway). "Vegetable oil" in recipes basically means "neutral oil, we just want the fat".
@Jefromi I don't know what country you live in, so I'm not going to categorically state that you are wrong, but all vegetable oil means is that you are certifying that the oil was obtained from a plant source. All lipids are capable of carrying fat soluble flavors. Soybeans contain more of those compounds than rapeseed does. Therefore, soybean oil has a more pronounced flavor than rapeseed oil does. In an application where you are tasting the oil directly (not indirectly as in a fried food), that taste difference is important.
@sarge_smith Okay, I should say: everything commonly sold in stores in the US as vegetable oil is essentially neutral, because the expectation is that it's going to be used as a general purpose oil, from sauteeing to baked goods. I doubt most people could tell the difference between the flavor of soybean and canola oil (it's *really* tiny), and vegetable oils are generally used in things where whatever subtle flavor the oil has is undetectable. This is almost certainly the case in the OP's party mix.
Vegetable oil is a category of oils, not a specific type. It could be palm, avocado, or many others. What is typically sold as vegetable oil in stores is soybean oil.
My guess is that soybean oil will work as a substitute for what you're doing, but that canola oil may be somewhat healthier.