Korea's oil exchange prints two prices for the same fuel, and they disagree four days in ten

Ask for “the Korean oil price” and Korea’s own exchange will hand you two numbers. Not a bid and an ask — two settled, published, weighted-average prices for the same fuel on the same day. One is the average of trades struck in the competitive auction; the other, the average of trades done by negotiation. Most days they sit close. Often enough to matter, they do not.

Two prices, and they disagree

The KRX petroleum market lists diesel, petrol and kerosene, and for each it prints both a competitive-auction average and a negotiated average every trading day. We took all 1,619 days from the start of 2020 to 6 August 2026 and asked a simple question: when both prices exist, how often is the negotiated one below the auction?

Close to four days in ten for diesel, closer to five for petrol and kerosene, the negotiated market clears under the auction. The reflex is to assume a negotiated deal costs more — you are paying for size, or for certainty. Here, nearly half the time, it costs less.

The typical gap is small. Take the median across every day both prices exist and the negotiated price sits just above the auction — by 5.0 won a litre for diesel, 1.6 for petrol, 0.9 for kerosene. But the median hides the spread. Day to day the gap runs across roughly two hundred won in either direction; a fuel that averages a one-won premium can trade a hundred won cheaper on Tuesday and a hundred won dearer on Thursday. The two prices track each other loosely, not tightly.

The auction that isn’t always there

The second column is the quieter finding. The competitive-auction price is not missing because of a holiday — the market was open and the negotiated price printed. It is missing because no auction trade happened at all that day.

For diesel and petrol that is rare, one day in twenty or so. For kerosene it is one day in six. Kerosene’s competitive auction is thin enough that, again and again, the only price the market can quote is a negotiated one. On 6 August 2026 that is exactly what you see: diesel and petrol each carry both prices, and kerosene carries a single negotiated figure — 1,381.73 won a litre — with the auction column blank.

So the honest version of “the kerosene price” is narrower than it sounds. One day in six there is no auction reference for it; there is only what two parties agreed.

Why this is worth a column

None of this says the exchange is broken. Two prices for two ways of trading is exactly what a competitive market and a negotiated market are supposed to produce, and publishing both is more honest than blending them into one number that hides the difference.

But it does mean “the KRX oil price” is not a single thing you can quote without choosing. The two are not interchangeable: they disagree in direction, not just size, on a large minority of days, and for kerosene one of them is often simply absent. Anyone building off these figures — an index, a contract reference, a chart — is picking one market over the other, whether they know it or not. The least a data source can do is say which, and how often the choice would have mattered.