* Crude futures settle higher, U.S. gains more than Brent * Brent/U.S. crude spread seesaws, then narrows below $9/bbl NEW YORK, May 16 (Reuters) - Cash crude differentials in theUnited States were mixed on Thursday as the transatlantic spreadbetween Brent and U.S. crude futures seesawed before narrowingand ending back below $9 a barrel, traders and broker said. In the futures market, Brent's premium to U.S. crude ended at $8.64 a barrel based on June contractsettlements. It ended on Wednesday at $9.38 after a close at$7.65 on Monday, the lowest the Brent premium has been atsettlement since Jan. 20, 2011, when it ended at $6.99. Brent's June contract expired on Thursday. The premium fell to $8.16 and reached $10.10 duringThursday's session. It fell to $7.20 during Tuesday's session,the lowest since Nov. 17, 2011, when it fell to $5.58 intraday. On Thursday, the spread between July Brent and U.S. crudecontracts was at $8.33 a barrel based on settlements. Usually the wider the arbitrage, the more supportive forU.S. cash crude differentials while a narrower spread oftenpressures differentials. This holds especially for sweet gradesthat are priced in line with other global waterborne crudes suchas Brent. Crude futures rose on Thursday, with Brent managing only a12-cent gain as it's contract approached expiration. The weakerdollar was credited with supporting dollar-denominated crude. CASH CRUDE VALUES In the U.S. cash crude market on Wednesday, Light LouisianaSweet for June delivery traded at $10.70, $10.75 and$10.85 a barrel over the U.S. June crude futurescontract, also known by its crude grade of West TexasIntermediate (WTI). WTI is the U.S. light, sweet crude contract's benchmarkgrade deliverable at Cushing, Oklahoma. Those LLS trades had stronger differentials afterWednesday's trades completed from $9.95 to $10.15 per barrel. Heavy Louisiana sweet traded at $10.20 and $10.30over the benchmark futures, stronger than offers from sellerspegged on Wednesday at $9.40 over the benchmark. A Gulf of Mexico-produced grade, Mars sour , had Junebarrels traded at $5.15 above the benchmark futures, strongerafter Wednesday's trade at $5.00 above the benchmark. Poseidon crude traded at $4.80 above the benchmarkfutures, within the bid/offer spread pegged on Wednesday at$4.45-$5.00 over the benchmark. MIDLAND GRADES West Texas Intermediate crude at Midland traded at30, 40 and 45 cents over the benchmark futures, little changedfrom Wednesday's trades completed at 40 and 45 cents over thebenchmark. Trades on Tuesday were completed at 30 and 35 centsover the benchmark. West Texas Sour crude, also at Midland, traded at 25and 30 cents over the benchmark, weaker after trading Wednesdayat 40 cents over. WTS traded on Tuesday at 30 cents over. Midland crude grades have had differentials above thebenchmark futures recently on support from expectations for andthen last week's restart of a crude distillation unit at ValeroEnergy Corp's McKee, Texas, refinery. Also supporting Midland differentials in recent weeks wereincreases in pipeline capacity from the West Texas region to theU.S. Gulf Coast's refineries, traders said. CRUDE FUTURES SETTLE HIGHER Expiring Brent June crude rose only 12 cents, or0.12 percent, to settle at $103.80 a barrel, having traded from$102.95 to $104.40. U.S. June crude rose 86 cents, or 0.91 percent, tosettle at $95.16 a barrel, having traded from $93.23 to $95.57.The U.S. June contract expires May 21. (Reporting by Robert Gibbons; Editing by Bob Burgdorfer)