They had some pretty senior people there, and it seemed like they met with a lot of people to talk about the market and their rationale for their position, one base oil buyer said.

Observers say ExxonMobil officials appeared to feel compelled to explain why prices are not out of whack despite the fact that gross refining margins – calculated as the difference between base oil prices and crude oil costs – are much higher than normal. These observers say ExxonMobil, along with other suppliers, have been pressing their case recently that crude has become a less reliable gauge of base oil costs since vacuum gasoil – the immediate feedstock for base oil – moved higher in relation to crude this year.

Suppliers are also noting that costs are up for natural gas, a key source of energy for refining. And while demand has been lackluster this year, supply has been significantly crimped by a series of operational disruptions.

According to some buyers, the jury is still out on the new paradigm. Customers are mulling supplier explanations and trying to test them with their own research. Some said their efforts are complicated by the fact that widely recognized sources of VGO prices are hard to find.

Petro-Canada said yesterday that it has finished repairs at its Mississauga, Ontario base oil plant and will resume normal operations this week. The 12,500-barrel-per-day plant has been operating at half capacity since an explosion Aug. 21. In addition, the plant was down the week leading up to the explosion because of a power blackout.

The price of crude oil on the New York Mercantile Exchange closed at $29.61 per barrel yesterday, 66 cents lower than a week earlier.