Placing the 9 February and 19 October Asia base oil assessments side by side makes the reading obvious. Group I SN150 ex-tank Singapore went from 790 to 830 US dollars per tonne to 1,500 to 1,540, close to 1.9 times; Group II 150N FOB Asia from 720 to 760 to 1,520 to 1,560, about 2.1 times; Group II 500N from 750 to 790 to 1,560 to 1,600, about 2 times; and Group III 4 cSt FOB Asia from 1,090 to 1,130 to 3,650 to 3,690, roughly 3.3 times. Same direction, a full tier apart in magnitude. Converted at roughly 159.54 yen to the dollar in late October, SN150 ex-tank sits near 243,000 yen per tonne, which is close to a doubled domestic-currency bill for a Japanese buyer.

The split traces back to where capacity sits. Argus puts the Middle East Gulf at about a fifth of global Group III capacity, supplying 47% of US and 72% of European Group III imports in 2025; when plants there stop, no substitute of comparable scale exists and price elasticity is at its worst. Group I and Group II output is spread across many Asian refiners, with ENEOS, GS Caltex, Petronas, CNPC and IOCL all on the anchor-supply list, and those refiners can switch crude slates to keep running, which is why Asian Group II eased from May onward. Put plainly, the higher the grade, the weaker the substitution elasticity and the larger the multiple. That is not speculation; it is what the capacity map produces.

Supply is also tightening in concrete, named ways. The sole Taiwanese producer began a turnaround at its Mailiao Group II plant on 12 October, cutting contract allocations and pulling its spot offers from the market almost entirely. A major South Korean exporter curtailed heavy base oil exports in October in favour of other products with better margins. The broader transmission runs through refinery slate economics: when gasoil and jet pay better, base oil availability falls as a co-produced stream, and with December Brent at 107.90 US dollars per barrel on 19 October the cost side offered no relief. Each of these items is specifically identified in the weekly reports of the period rather than inferred.

Operationally, four points for buyers participating in this market. First, classify by formulation: most industrial hydraulic oils, gear oils and greases are built on Group I and Group II mineral base stocks and carry the 1.9 to 2.1 times move, while low-viscosity engine oils and many synthetic blends lean on Group III and carry the 3.3 times move, and skipping that split leaves the cost model wrong by construction. Second, write both a quotation validity window and the named public assessment it tracks into every offer, since with prices still moving weekly an offer missing either carries very high risk. Third, confirm lead times grade by grade rather than running one lead time across all SKUs. Fourth, SNSUC's addressable scope is SN150 and SN500 base oil, paraffin and finished lubricants, with hazardous chemicals excluded from all discussions. A closing caution: this is market observation based on public data and not investment advice, and different price bases, Singapore ex-tank versus Asia FOB, are not interchangeable.