WTI and Brent are both light sweet crudes of broadly similar quality, and their prices track closely. Almost everything interesting about them is in the differences.

WTI is landlocked. It is deliverable at Cushing, Oklahoma, an inland tank farm connected by pipeline, and physically settled there. That makes it a genuinely local price: pipeline outages, refinery turnarounds in the mid-continent, and Cushing tank levels all move it for reasons that have nothing to do with world oil. Brent is waterborne and financially settled against an index of North Sea assessments, so it responds to seaborne supply and demand and can be arbitraged against other waterborne grades by chartering a ship.

The spread between them is therefore not a quality spread, or not mainly. It is a location spread, and its natural anchor is the cost of moving a barrel from the US Gulf Coast to Europe. When US production and export capacity are ample, the spread sits near that freight cost. When something constrains the movement, it moves away from it.

Brent - WTI  ~  USGC-to-Europe freight + quality adjustment

freight: the marginal cost of moving the barrel, which varies with tanker rates
quality adjustment: small, since both are light sweet

An anchor, not an identity. The spread departs from it whenever the movement is constrained at either end.

The history is worth knowing because it explains why the spread is not stationary. Before US shale, WTI usually traded at a small premium to Brent, since Cushing was a consuming hub. Shale reversed it: mid-continent production overwhelmed pipeline capacity out of Cushing, barrels backed up, and WTI traded at a deep discount for years. The lifting of the US crude export ban and the build-out of Gulf Coast export capacity then re-anchored the spread to freight. Three distinct regimes, one ticker.

XBMCross-BenchmarkLIVE FROM THE DESKOpen on the desk

WTI against Brent across the curve, so a structural divergence is visible rather than inferred from the front spread alone.