The complaint does not name the two lubricant suppliers but an association official identified them as ExxonMobil and Castrol, emphasizing that the association has no objection with them.

The complaint says the lock-out endured for a year before any of its members obtained Volkswagens certification. The association did not specify the amount of damages it seeks, saying it would leave that for the commission to determine. An official, who spoke on condition that he not be identified, said the association considers the case significant not only for the business that members lost but also because of the precedent it could establish.

We made this complaint mainly on principle, because if we accept this action today, tomorrow Volkswagen or maybe another OEM could establish a similar arrangement, the official said.

A Volkswagen spokesman said the company would not comment because the matter is pending.

According to the lubricant group, European Commission regulations allow automakers to set requirements for lubricants used in their vehicles but not to endorse particular suppliers to the exclusion of others. The regulations do allow automakers to contract individual suppliers for spare parts but lubricants and other consumables fall outside the definition of spare parts.

The lubricant group claims that Volkswagen does not dispute its allegations but claims that any economic advantage derived by ExxonMobil and Castrol was justified by their investment of up to EUR 1.5 million (US$ 1.35 million) to develop the products.

The association noted that Volkswagen twice before has been found in violation of commission rules on anti-competitive practices. The commission could take two or three years to render a decision on the current complaint.