Everyone talks about barrels of Iranian oil, but very few people understand what is actually inside those barrels. This difference is the reason why Western refineries have, for nearly twenty years, continued to obtain Iranian oil through hidden trading networks via Dubai, despite sanctions.
Crude oil is not a single uniform substance. It is actually a mixture of different hydrocarbon molecules with varying weights and structures. This composition determines how easily a refinery can convert it into gasoline, diesel, jet fuel, and heating oil.
To measure this, a scale called API Gravity is used.
A higher API Gravity means lighter oil, which is easier and cheaper to refine and produces a higher yield of valuable fuels.
A lower API Gravity means heavier oil that requires more energy, more processing stages, and expensive industrial infrastructure to refine.
Iran’s Iranian Light crude typically ranges between 33 and 36 API Gravity, with a sulfur content of about 1.36% to 1.5%. This balance is what the refining industry calls the “sweet spot.”
It is light enough to produce large amounts of gasoline and diesel, yet heavy enough to allow refineries to produce various types of fuels. That is why petroleum engineers often describe it as an Optimal Blend Crude.
Now compare it with other oils.
Venezuela’s Merey heavy crude has around 16 API Gravity and sulfur levels between 3% and 5%. Refining it profitably requires complex equipment such as coking units, hydrocrackers, and large desulfurization systems. Therefore, it is not a substitute for Iranian oil but a completely different type of crude.
The United States produces West Texas Intermediate (WTI), which has about 39 to 40 API Gravity and very low sulfur—less than 0.25%. In theory, this makes it very clean and easy to refine. In practice, however, it is often too light for many large refineries. Many refineries in Europe and Asia frequently blend it with heavier crude oils to make it suitable for processing.
This is why Iranian oil occupies a special position in the global refining system. It is neither too heavy nor too light. This balanced composition makes it extremely suitable for refineries worldwide.
For this reason, many countries—particularly refineries in India—have continued to look for ways to purchase Iranian oil despite sanctions. That is also why secret trading and financial networks developed through Dubai.
That is why the Strait of Hormuz is not just a passageway for oil shipments. It is a corridor for a specific type of crude oil that keeps much of the world’s refining system running efficiently.
If this route were to close, it would not only reduce the quantity of oil available, but it would also remove a particular type of crude oil that most of the world’s refineries are designed to process.
This is why when oil prices rise to around $82 per barrel, the price does not only reflect the quantity of oil—it also reflects the molecular quality of that oil.
