The standout on the board today is fuel oil. The front-month contract printed ¥5,054/t, +15.49%, erasing the post-holiday pullback in one session. Bitumen trailed at ¥5,406/t, +6.19% — the two heavy-end chains moving in step.

Rubber told a less unified story. Butadiene rubber reached ¥16,350/t, +3.02%, while natural rubber managed only ¥20,020/t, +1.57%. Synthetic rubber tracks crude and butadiene; with crude up and naphtha cracks tight, butadiene had a cost tailwind. Natural rubber is capped by the Yunnan and south-Thailand tapping peak, where spot premiums cannot build, so its catch-up was throttled.

What the split means for the desk: heavy-end strong, natural-end weak pulls cross-commodity spread money toward fuel oil. Among our 13 listed categories, bitumen and fuel oil sit in the tradable energy-chemical bucket; today's move lifted the grade coefficient in the posting formula (Brent × FX × 7.33 × grade), and the quoting engine will reprice them once this afternoon.

One caveat: a +15.49% single-day print on fuel oil is mostly near-month rollover plus short covering, not a genuine spot squeeze. Watch warehouse-receipt cancellation speed next week before drawing conclusions — do not chase a heavy-end position at these levels.