"If you hit a vein with, say, 1ml of oil, blood flow will carry the oil to the heart. The heart will then pump it to the lungs for gas exchange, but the gas exchange can't happen because the blood has been replaced with oil. The oil will stick in that spot in the lungs, resulting in a hard, nasty cough. In addition, the heart will beat profusely as it tries harder and harder to produce some gas exchange. I know a very reputable source who told me that injecting as little as 3ml this way has resulted in death."
from a bodybuilding website on injecting testosterone and other oil-based steroids IM
"ARE YOU SURE IT WILL HURT ME IF I INJECT INTO A VEIN?

Not only yes, but hell yes. First, the T isn't what hurts you, it's the oil the T is suspended in, that's the culprit. WHY? On the way to the heart, the oil can cause a blood clot and if it doesn't it probably will when it gets into the heart chambers. If you develop a clot in the leg, you could lose the leg. If a clot forms in the heart muscle, you could have a heart attack. If a clot were to form and get to the brain, stroke is a real threat. You could die, no kidding."
from an FTM site