Base oil prices have climbed at a dizzying pace the past six months, spurred by rising crude oil and feedstock costs. Motiva appeared to trigger the sixth round of increases when it announced a 14-cent increase for Aug. 18, just seven days after its previous markups.

Flint Hills Resources was quick to follow, with an identical increase on Aug. 19, and Calumet announced a few days later that it would raise its prices 10 cents, effective today.

A lull came next, however, with other suppliers seeming to wait for action by Group I leader ExxonMobil. By the beginning of this week, some observers were speculating that ExxonMobil might stand pat for the time being. One marketer noted that costs for feedstock vacuum gas oil – which jumped approximately 25 cents per gallon during the first half of the month – gave back approximately 15 cents per gallon in the two days after Motivas announcement.

ExxonMobil finally moved yesterday, sources said, announcing its whopping 15-cent hike on all posted prices. By days end, ConocoPhillips said it would add between 14 cents and 17 cents per gallon to its Group II and Group III stocks. Other suppliers were expected to announce increases in coming days.

Naphthenic suppliers moved in a tighter group. Volume leader Ergon said Monday that it will hike prices for all products by 10 cents on Aug. 29. Nynas, Calumet, Cross and San Joaquin Refining all jumped in by the close of business yesterday, saying they will impose increases of equal amounts. Nynass is scheduled for Aug. 29, Calumets and Crosss for Sept. 2. San Joaquin has not yet made a formal announcement, but said its eye is on mid-September.

The price of crude on the New York Mercantile Exchange closed yesterday at $66.20 per barrel, according to Bloomberg. That was 10 cents lower than a week earlier.

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