Sept. 29 (Bloomberg) -- U.S. Gulf crude premiums weakened after the discount for West Texas Intermediate versus Brent narrowed.

The gap between WTI and Brent November contracts decreased 79 cents to $21.81 a barrel in New York. The spread settled Sept. 6 at a record margin of $26.87.

When Brent decreases versus WTI, it weakens the value of low-sulfur U.S. grades that compete with West African oil priced against the European benchmark.

Heavy Louisiana Sweet’s premium to WTI declined $1 to $25.25 a barrel at 1:59 p.m. in New York, according to data compiled by Bloomberg. Light Louisiana Sweet’s premium dropped 65 cents to $24.10.

Among sour, or high-sulfur, grades, the premium for Mars Blend lost $1 to $21 a barrel while Poseidon weakened 65 cents to $20.85 a barrel over WTI.

Southern Green Canyon’s premium narrowed 75 cents to $19.75 a barrel and West Texas Sour’s discount was unchanged at 90 cents a barrel below WTI. Thunder Horse’s premium lost 60 cents to $25 above the benchmark.

The premium for Syncrude was weakened 90 cents to $7.75 a barrel, the smallest since July 1. Syncrude is a light, low- sulfur synthetic oil derived from the tar sands in Alberta.

The discount for Western Canada Select widened 5 cents to $10.50 a barrel.

--Editors: David Marino, Bill Banker

-0- Sep/29/2011 19:26 GMT

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 -0- Sep/29/2011 19:14 GMT