Canadian oils gained a day after Exxon Mobil Corp. (XOM) said it completed maintenance work at its Montana refinery.

Pam Malek, a Billings, Montana-based spokeswoman for Exxon, declined to say yesterday when the maintenance began. The refinery buys crude from suppliers in Wyoming and Alberta, according to a brochure for the refinery.

Western Canada Select’s discount to West Texas Intermediate narrowed 75 cents to $19.50 a barrel at 2:05 p.m. in New York, according to data compiled by Bloomberg. Syncrude’s discount narrowed 25 cents to $4 below the U.S. benchmark.

Bakken oil’s discount was unchanged at $7.50 a barrel.

U.S. Gulf Coast crude grades were mixed. Light Louisiana Sweet’s premium to WTI lost 5 cents to $11.85 a barrel. Heavy Louisiana Sweet’s premium decreased 5 cents to $14.75 a barrel.

Mars Blend’s premium was unchanged at $10. Southern Green Canyon’s premium rose $1.50 to $10.10. Poseidon’s premium narrowed 5 cents to $8.85.

The premium for Thunder Horse, a sour crude with lower sulfur content than Mars, Poseidon and Southern Green Canyon, added 20 cents to $11.20 a barrel.

To contact the reporter on this story: Aaron Clark in New York at aclark27@bloomberg.net

To contact the editor responsible for this story: Dan Stets at dstets@bloomberg.net