* Crude futures jump 1 percent as gasoline prices surge * Brent-U.S. crude spread seesaws, ends little changed NEW YORK, July 12 (Reuters) - Cash crude in the UnitedStates traded at differentials in a wide range on Friday,seesawing along with the transatlantic spread, traders andbrokers said. Brent crude's premium to U.S. crude ended at$2.86 a barrel based on August contract settlements, only afour-cent wider spread after it ended at $2.82 on Thursday. But the spread ranged from $2.41 to $3.36 on Friday and thespread on Thursday ranged from $1.32, the narrowest betweenfront-month contracts since November 2010, and $3.13. The stronger differentials for many trades completed forcash crude grades on Friday reflected the stronger Brentpremiums intraday. Usually, the wider the arbitrage, the more supportive it isfor U.S. cash crude differentials, while a narrower spread oftenpressures differentials. This especially holds true for sweetgrades, which are priced in line with global waterborne crudessuch as Brent. Crude futures settled 1 percent higher on Friday, erasinglosses as gasoline futures surged on concerns that a string ofrefinery outages in North America. CASH CRUDE TRADES Light Louisiana sweet crude oil for August deliverytraded on Friday from $4.70 to $5.20 over the benchmark U.S.August crude futures. That range for differentials was stronger than Thursday'strades completed from $4.60 to $4.90 over the benchmark. Mars sour crude, a Gulf of Mexico-produced grade,traded from $1.20 to 90 cents under the futures benchmark, astronger range than Thursday's trades at $1.40 to $1.20 underthe benchmark. Southern Green Canyon (SGC) crude traded at $2.00 and$1.70 under the futures benchmark, after Thursday's trades at$2.10 under the benchmark. Friday's range was closer to Wednesday's, when SGC traded at $1.80 and $2.00 under the benchmark. MIDLAND GRADES West Texas Intermediate crude at Midland traded at 55and 45 cents under the futures benchmark on Friday, aftertrading on Thursday at 55 and 60 cents under the benchmark. West Texas Sour crude, also at Midland, traded at 20cents under the benchmark, stronger after Thursday's trade at 5cents under. CRUDE FUTURES Brent August crude rose $1.08, or 1.0 percent, tosettle at $108.81 a barrel. U.S. August crude rose $1.04, or 0.99 percent, tosettle at $105.95 a barrel. (Reporting by Robert Gibbons)