* LLS drops $1.10 to sell at WTI plus $21.40
* Mars trades at WTI plus $14.50, down $1.40
* WTI-Brent spread trades in narrow range
By Janet McGurty
NEW YORK, April 5 (Reuters) - U.S. Gulf Coast cash crude differentials fell on Thursday as the transatlantic arbitrage moved in and traders looked to finish buying before the long holiday weekend.
Light Louisiana Sweet sold down $1.10 to trade at $21.40 a barrel over West Texas Intermediate.
Mars Sour traded at $14.50, down $1.40 while West Texas Sour traded at $9.00 under WTI, a loss of 35 cents.
West Texas Intermediate at Midland shed 80 cents to trade early at $9.00 under WTI but then trade thinned due to a lack of offers.
"The arb is somewhat (influencing prices) and folks are getting their weekly supplies done. The biggest thing I've noticed is that some of the crazy, aggressive traders have been almost silent with some suggesting they are in Atlanta at the Masters," said John Troland, an independent oil consultant based in Houston, referring to a golf tournament under way.
The transatlantic spread stood at $20.07 in favor of Brent. The spread settled at $20.87 in favor of Brent on Wednesday.
U.S. May crude rose $1.84, or 1.81 percent, to settle at $103.31 a barrel, having traded from $101.37 to $103.40. For the week, crude gained 29 cents, or 0.28 percent.
In London, Brent May crude rose $1.09, or 0.89 percent, to settle at $123.43 a barrel, having traded from $121.80 to $123.52.