Please guys, stop saying aspirating is not necessary: it's dangerous not doing so and if you inject into a vein the oil will be pumped straight into your heart and then your lungs and from what I've heard from people who've had this happen, BECAUSE IT HAPPENS, it feels like you're gonna die and collapse and stuff.
The leason to learn here is to keep your hand strong and steady so the needle doesn't move after you've aspirated and you know you really are injecting into the muscle.