Can you have straight up garlic oil?
Garlic oil; that is, oil directly from garlic is certainly a thing.  It is usually achieved using steam distillation.  I have read that the undiluted oil has about 900 times the strength of fresh garlic.  That's generally much more potent than any home cook or chef wants to deal with. For the vast majority of culinary applications, garlic is used to flavor oil.  Any oil will work, and the way the garlic is chopped (or not), as well as how it is heated (and how long) in the oil, will have significant impacts on the final result.