Analysis: Tesoro’s California refinery deal probed by regulators →

WASHINGTON, Feb 14 (Reuters) – Tesoro Corp., one of California’s biggest gasoline producers, has made an aggressive play to buy a BP refinery in southern California but winning antitrust approval will be no slam dunk.

Tesoro announced in August that it had agreed to buy BP’s Carson plant for $2.5 billion, creating the biggest oil-refining empire in the Pacific Basin with about a quarter of California’s processing capacity.