Some suppliers have suggested in recent weeks that the rash of price hikes was at least partly due to announcements by Shell Oil Products US that it plans to close its base oil plants at Deer Park, Texas, and Martinez, Calif., in March and August, respectively. Together, those plants account for 20 percent of U.S. naphthenic capacity, and Shells announcements have reportedly sent customers scrambling.

Sources reached this week, however, maintained that prices are rising solely because of crude costs.

This is all because of crude, one marketer said. Suppliers have seen some significant increases in raw materials costs and were simply trying to pass those on to our customers.

Crude prices were little changed from last week. The price on the New York Mercantile Exchange fell 55 cents yesterday to close at $36.72 per barrel.

Sources expressed differing opinions about whether Shells closings will push naphthenic prices higher. Some argued that the market has long been over supplied and that the reduced production will merely bring it into balance. Others said the loss of so much capacity is bound to have an impact.

There seems to be plenty of naphthenic oil available now, a marketer said. But I think youre going to see prices go up more, maybe after the first closing, certainly after the second.

Calumetadded 5 cents to its paraffinic base oil postings, effective March 3. Citgo also implemented a 5 cent hike Feb. 27.

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