* Crude futures end down, but well above intraday lows * Brent/U.S. crude spread narrows, ends back below $8/bbl NEW YORK, May 10 (Reuters) - Cash crude differentials in theUnited States were mixed on Friday, as the transatlantic spreadbetween Brent and U.S. crude futures seesawed before narrowingslightly, dropping back under $8 a barrel. Both Brent and crude futures ended lower, but well abovesession lows. In the U.S. cash crude market on Friday, Light LouisianaSweet for June delivery traded from $9.10 to $9.40 overthe U.S. June crude futures contract, also known by its crude grade of West Texas Intermediate (WTI). WTI is the U.S. light, sweet crude contract's benchmarkgrade deliverable at Cushing, Oklahoma. Those LLS trades were complete at differentials either sideof Thursday's trade at $9.25 above the benchmark. Wednesday'strades also were done at a wide range, from $9.05 to $10.00above the benchmark. A Gulf of Mexico-produced grade, Mars sour , had Junebarrels traded at $4.00 and $4.50 above the benchmark futures,after trading on Thursday from $4.00 to $4.40 above thebenchmark. Mars traded at $4.15 over for July barrels and at $3.80above the benchmark for August barrels. Eugene Island traded at $6.70 over the benchmarkfutures, after trading on Thursday at $6.50 and $6.60 over. MIDLAND GRADES West Texas Intermediate crude at Midland had itsbid/offer spread pegged at 10/20 cents over the benchmarkfutures, after trading on Thursday traded at 5 and 15 centsover. The differential has weakened from Monday, when trades werecompleted in a much stronger range from 35 to 65 cents over. West Texas Sour crude, also at Midland, traded at 15cents over the benchmark, stronger after trading Thursday at 5cents over the benchmark. The differential has weakened from 60cents over on Monday at 60 cents over. After Midland crude grades were recently supported by therestart of a crude distillation unit at Valero Energy Corp's McKee, Texas, refinery, expectations that anotherMidwest crude unit restart is pending could help differentialsstrengthen, traders said. BP Plc's Whiting, Indiana, refinery should begin oilflows through its 240,000-barrel per day crude unit early nextweek, according to IRR Energy. The BP unit restart will take more oil out of the Cushinghub, helping relieve the glut of crude in the region. 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. BRENT/WTI SPREAD Brent's premium to U.S. crude ended at $7.87 abarrel on Friday based on June contract settlements, afterending at $8.08 on Thursday. The premium was as low as $7.62 during Friday's session andreached $8.45. On Wednesday, the spread ended at $7.72, the narrowest atsettlement since Jan. 20, 2011, when it ended at $6.99. Brent's premium fell to $7.58 during Wednesday's session,the lowest it had been since Dec. 28, 2011, when it fell to$7.31 intraday. Usually the wider the arbitrage, the more supportive forU.S. cash crude differentials while a narrower spread oftenpressures differentials. This holds especially true for sweetgrades that are priced in line with other global waterbornecrudes such as Brent. CRUDE FUTURES FALL Brent June crude fell 56 cents, or 0.54 percent, tosettle at $103.91 a barrel, having traded from $101.56 to$104.45. U.S. June crude fell 35 cents, or 0.36 percent, tosettle at $96.04 a barrel, having traded from $93.37 to $96.24. (Reporting by Robert Gibbons; Editing by Kenneth Barry)