The cleanest signal today: the heavy-oil chain and the rubber chain are running on two separate lines. Fuel oil at ¥5,386 and bitumen at ¥4,965 rise 2.83% and 4.79% respectively on real volume-backed gains, while natural rubber at ¥19,365 gives back 1.63% and butadiene rubber at ¥16,660 adds 1.83%. Same chemicals label, already split inside.

The cause sits in cost structure. Bitumen and fuel oil anchor to crude and plant runs; crude fell on both sides today yet neither followed, because refinery maintenance season tightened supply and opened the crack spread. On the rubber side, natural rubber tracks seasonal tapping and bonded inventories while butadiene rubber tracks the butadiene monomer, so the two decouple — one down, one up, no contradiction.

For SNSUC's data framework, forcing thirteen categories onto one benchmark would hide this split. We actually split the board into a heavy-oil crack curve and a synthetic/natural rubber curve, weight them separately, and calibrate the grade factor in the listing formula (Brent × FX × 7.33 × grade) along those two lines rather than applying Brent across the board.

On the procurement side: do not chase and lock volume on heavy-oil grades today, wait for maintenance-season supply to return; within the rubber chain, natural rubber's pullback is a staged-build window while butadiene rubber's gain should be confirmed against the monomer quote first.