Fuel oil closed at ¥4,911/t, up 2.4%, while bitumen at ¥4,533/t rose only 0.53%. On the surface it is a split inside the heavy-oil complex; underneath, it is a demand-structure story — fuel oil pulled by bonded bunker restocking, bitumen held down by road off-season.

Zhoushan's push to capture international transshipment bunkering has not let up. Foreign-flag vessels call to lift VLSFO, eating into the regional premium. The result is a narrower Zhoushan VLSFO premium to the Singapore 0.5% sulfur swap; a tighter spread pulls more ships to divert and refuel, a self-reinforcing loop.

On the domestic heavy-oil side, bitumen demand stays soft, so its price tracks only residual demand. That frees up blending feed for fuel oil — independents swing residue between coking and bunkering toward whichever side pays more.

For SNSUC's fuel-oil re-export book, a narrower Zhoushan premium makes delivered bunker cost more transparent, but it also ties the domestic supply price closer to the international swap. Locking volume means watching both the Singapore swap and Zhoushan physical, not one in isolation.