The biggest flow of crude on the planet runs from the Middle East to Asia, and it does not price off Brent or WTI. It prices off Dubai, usually as part of a Dubai-Oman complex, and the mechanism differs from the Atlantic basin in ways that matter.
Middle Eastern producers largely do not sell on a spot market. They sell on term contracts at an official selling price, set monthly by the producer itself, expressed as a differential to the relevant benchmark. Saudi Arabia's OSP is the best-known example. The buyer does not negotiate the differential; it is announced, and the buyer's choice is how much to lift within contractual limits.
That makes the OSP an unusual and informative object. It is a producer's own statement about the relative value of its grades in a given region, published monthly, and it is one of the few things in the market that is a decision rather than an outcome. A widening OSP discount into Asia is a producer competing for market share; a narrowing one is a producer that believes demand is strong enough to bear it.
The quality profile is different too. Dubai is medium sour, unlike the light sweet Atlantic benchmarks, which makes it the appropriate reference for the grades that actually move on that route. This is why the Brent-Dubai spread is watched: it is a light-sweet-versus-medium-sour spread and a west-versus-east spread at the same time, and it governs whether Atlantic basin barrels can compete in Asia. When it widens enough to cover freight, the arbitrage opens and cargoes redirect.
Murban has been added to the complex as an exchange-traded, deliverable Abu Dhabi grade, which is an attempt to bring exchange-style price discovery to a market historically priced by assessment and OSP. Whether it accumulates enough liquidity to matter is still an open question, and it is the same question every new benchmark faces.