BANGOR, Maine — Bob Graves, owner of an Exxon gas station on Hammond Street for more than a quarter of a century, recently was forced to abandon his relationship with Exxon-Mobil for a new relationship with Citgo, and he’s not alone.

“It’s happening all over the New England region,” said Rob Vaker, owner of Broadway Citgo, located on the corner of Broadway and Griffin Road, which sold Exxon gas until recently.

“The official change happened on Feb. 28. It’s part of that merger [of Exxon and Mobil] years ago,” which required Exxon-brand gas sales to cease in Maine, he said.

When the Exxon-Mobile merger was approved in 1999, the Federal Trade Commission required the new company to divest itself of approximately 2,000 gas stations of about 14,000 total in the U.S. within 10 years. The company decided to do so in the Northeast, and that includes the pullout of Exxon stations from Maine.

“The federal government said it would be one or the other,” Graves said. “There is still Exxon, but not in this part of the country. Exxon had to leave the Northeast. Where you find Exxon, there is no Mobil.”

The Hammond Street gas station, constructed in 1941, sold Exxon gas products even before Graves took ownership in 1982, he said.

“Years before that, it was [an] Esso” station, he said.

Both Bangor gas station owners knew the change was coming, but neither is happy about the Exxon pullout. Both have contracts with Webber Energy, which does not supply Mobil products, so they say they had to make a change.

“We had no option” but to switch, Graves said.

Calls to Mike Shea, president and CEO of Webber Energy, to find out why Webber doesn’t carry Mobil products, and to the public affairs office of Exxon-Mobil, headquartered in Texas, were not immediately returned on Monday.

While most of the Exxon gas station departures happened in New England, a few occurred in New York and as far away as Virginia. Exxon-Mobil announced Exxon’s planned departure from Maine last year.

Vaker said he chose Citgo Petroleum Corp. because he has a Mobil next door and two Irving Oil gas stations nearby. He had a choice of providing Gulf Oil, Sunoco Oil, Valero Energy Corp., Shell Oil Corp., Irving or Citgo products through his fuel agreement with Webber, he said.