The most likely outcome of an embargo on oil purchased from Iran is that the countries participating in the embargo buy less oil from Iran while other countries not participating in the embargo buy more oil from Iran ([1], [2]). While this would produce some dislocations, if total world oil production doesn't change, it would have little effect on either Iran or oil-consuming countries, and would basically be a symbolic gesture.
Scary Part?
And each of these events was also followed by a recession in the United States. The table below summarizes the average annual growth rate of U.S. real GDP in the 5 quarters following the above oil price increases. Instead of growing at the historical average of 3.2% per year, U.S. real GDP fell in each case.
Iranian oil embargo
