What an OSP actually is — and isn't
Most news coverage treats the Arab Light OSP as a price. It is not a price — it is a differential. Aramco does not set an absolute dollar figure for its crude. It sets a premium or discount against a regional benchmark: Oman/Dubai average for Asian buyers, ICE Brent for European buyers, and the Argus Sour Crude Index (ASCI) for North American buyers.
What Aramco actually publishes every month — around the 5th — is a number like "+$3.90 vs Oman/Dubai average." The absolute price a buyer pays is that differential plus whatever Oman/Dubai is trading at when the cargo actually loads. This is why the OSP differential and the absolute price move independently. In a normal market, the differential tells you Aramco's view of its crude's value relative to alternatives. In the current crisis, it tells you something more complicated.
Aramco's monthly OSP sets the pricing trend for the region. Kuwait, Iraq, and Iran all price their crude with reference to Aramco's OSP. When Aramco raises the Arab Light differential by $2.40, as it did for March 2025, Kuwait, SOMO, and QatarEnergy typically follow within days. Aramco is not just pricing its own crude — it is setting the regional price level for roughly 9 million barrels per day of Asian-bound crude.
Arab Light OSP for Asia — 13-month differential history
The chart below shows the Arab Light OSP differential vs Oman/Dubai for Asian buyers. A positive number means Asian buyers paid a premium above the benchmark; negative means a discount. The current situation — a war premium replacing the normal demand-driven signal — is visible in the April 2026 reading.
The OSP signal decoder — what each move says
Every OSP move carries information beyond the number. Here is how to read the last 13 months.
Five grades — five signals
Aramco does not set one OSP. It sets five — one per crude grade. The spread between grades tells you which refineries are in demand and which crude types are scarce. When Arab Heavy trades at a large discount to Arab Light, it signals that complex refineries capable of processing sour heavy crude are in short supply or that Asian buyers are prioritising lighter, easier-to-process grades.
| Grade | API gravity | Sulphur | OSP diff vs Brent | March 2026 | Signal |
|---|---|---|---|---|---|
| Arab Super Light | >40° | ~0.06% | +$14.20 | ~$86.20 | Premium condensate — scarce, commands highest margin |
| Arab Extra Light | 36–40° | ~0.07% | +$13.10 | ~$85.10 | High naphtha yield — valued by petrochemical refiners |
| Arab Light | 32–36° | ~1.8% | +$11.84 | ~$84.00 | Flagship grade. Regional benchmark. Sets trend for Iraq, Kuwait, Qatar. |
| Arab Medium | 29–32° | ~2.6% | +$9.20 | ~$81.20 | Requires complex refinery. Discount to Light reflects processing cost. |
| Arab Heavy | <29° | ~2.9% | +$7.64 | ~$79.80 | Widest discount to Light in 18 months — complex refinery demand constrained |
Why +$11.84 is unlike any previous OSP cycle
In normal market conditions, a large positive OSP differential reflects Aramco's confidence in Asian demand, or a temporary tightening of sour crude supply, or competition-squeezing against UAE's Murban. The differential moves a dollar or two. It is a market signal.
The current +$11.84 Arab Light vs Brent differential is not a market signal. It is a crisis artifact. It reflects three simultaneous distortions that have never previously coincided.
First: the Brent benchmark itself is depressed relative to Gulf physical crude. Brent crude surged past $120 per barrel immediately after Hormuz closed , then fell back toward $72 as markets priced in reserve releases and uncertainty. But the Brent futures contract — which is the reference — is increasingly disconnected from Gulf physical crude, which cannot be transported to the North Sea delivery point because Hormuz is closed. The physical premium is real; the futures market is pricing something different.
Second: the Platts Oman/Dubai assessment — which underpins all Asian OSP calculations — was based on extremely thin trading volumes after March 2 , when war began. A benchmark built on near-zero transactions is producing artificial price signals. Indian refiners are now paying $45–50 more per barrel than they would under a properly functioning benchmark system.
Third: Saudi Arabia is the last seller standing. Saudi Arabia accounts for approximately 40% of Gulf oil flows that are still moving . With Iraq under force majeure, Kuwaiti exports severely curtailed, and UAE running at Fujairah bypass capacity, Aramco faces no competitive constraint on its OSP. It can raise the differential because buyers have no alternative.