Naphthenic production likewise was up-and-down over these same years. Pale oil production in the first six months of this year was just under 5.1 million barrels, down more than 10 percent from last years nearly 5.7 million barrels. In 2010, naphthenics output for the first six months was 5.2 million barrels.

Domestic refiners started 2012 on an optimistic note, but soon some were voicing concern that demand was more temperate than theyd hoped. Most years, refiners take advantage of weak demand in February to perform any needed maintenance work, then begin to ramp up production of base oils during March. This year, the EIA data show, it was April before base oil producers began their march upward.

Plant outages and turnarounds also nibbled away at refinery output in the first half, sources pointed out. On the naphthenics side, several refineries were taken down for maintenance in the first half, including Calumets 6,900 barrel per day site in Princeton, La., Cross Oils in Smackover, Ark. (5,000 b/d), and San Joaquin Refinings in Bakersfield, Calif. (8,100 b/d).

Paraffinic refineries had their turnarounds, too, starting with scheduled work in February at Calumets Shreveport, La., plant, which has 11,900 b/d of API Group I/II capacity, and Motivas Port Arthur, Texas, facility, which has 40,300 b/d of Group II capacity spread across three trains. And in Westlake, La., the 22,000 b/d Excel Paralubes Group II refinery had a turnaround which ran from March to the end of April, points out Jamie Brunk with Solomon Associates in Houston.

These planned downtimes may have dented output in the first half, agreed Stephen B. Ames, of SBA Consulting in Pepper Pike, Ohio. But remember, it doesn’t mean supply is more erratic-just that production is more erratic. These refineries, before they go into a turnaround, will fill their tanks so their customers don’t feel any disruption.

More disruptive to the smooth flow of barrels are unplanned outages, he says, such as the one that hit Motiva in May. On May 12, Port Arthur experienced a fire that knocked a lubes hydrotreater off line for a month. It had to put customers on 50 percent allocation of its Star 6 Group II until the repairs were complete.

The U.S. today has fewer players, and fewer but larger plants than it did 10 years ago, Ames observed. So when one goes down for a turnaround or has an operational problem, theres a much bigger impact on production than before. You can see it month to month, when you look at EIA’s data on total base oil output.

More than 80 percent of North America’s Group II capacity is concentrated now at just five sites, he pointed out. Besides Motiva, they include Excel Paralubes; ExxonMobil in Baytown, Texas; Petro-Canada in Mississauga, Ontario; and Chevron’s 20,000 b/d Group II plant in Richmond, Calif.-which is down now because of a fire in a crude unit last month.

In the Group I arena, five plants hold 75 percent of the nameplate capacity: ExxonMobils three (Baton Rouge, La., Baytown and Beaumont, Texas), HollyFrontier in Tulsa, Okla., and PBF Energy in Paulsboro, N.J.

And if you look at naphthenics there are only a few sizable players there too, said Ames. Cross Oil, Calumet, San Joaquin on the West Coast, and Ergon, the big dog.

Whenever any of the above goes down for more than a few days, the effects will likely be seen in the EIA data, he concluded.