An ExxonMobil spokeswoman told Lube Report that the company has refused to sell some customers more barrels than they previously said they would need.

We have contracted base stock customers that will get volumes they contracted for, spokeswoman Barbara E. Leatherwood-Gomez told Lube Report yesterday. We also have non-contracted customers. The base stocks they receive will be limited to their monthly averages year to date by grade.

Market sources said the action affects ExxonMobils supply of Group II-plus oils and heavy weight Group I stocks. The company is by far the biggest base oil supplier in North America and observers said it is unusual to see it place such limits.

Leatherwood-Gomez said the limits are due to strong demand and the need to replenish inventories after a winter maintenance turnaround at the companys plant in Baton Rouge, La. The company had said the shutdown went smoothly, without any mishaps that would affect production.

Observers said the situation presents a conundrum for some base oil purchasers.

Everybody makes projections, one source said. Sometimes youre high, sometimes youre low. Plus were into a season now when [lubricant] production tends to be higher, so blenders are probably wanting more base oil than they needed earlier in the year. So Im sure there are companies that are used to being able to get whatever they need from ExxonMobil, and they cant do that now.

Posted prices for paraffinic base oils are unchanged this week. The price of crude closed at $41.23 on the New York Mercantile Exchange yesterday, up $1.11 from a week earlier.

Historic U.S. posted base oil prices and WTI and Brent crude spot prices are available for purchase in Excel format.