Oil prices were higher today but underlying concerns remain, especially in the diesel market. A slump in U.S. refining activity and disruptions to global trade have tightened diesel supplies in recent weeks, dampening historically high U.S. diesel exports to Europe this month. U.S. diesel cracks briefly surged to a four-month high of more than $48 a barrel this month, crimping arbitrage opportunities to ship the fuel to Europe. While early trade on Monday was driven by fears about persistent inflation limiting demand, the focus moved to a more basic issue, said Phil Flynn, analyst and Price Futures Group. “We seem to be slipping back to the supply side issue,” Flynn said. “Demand is very strong and at the end of the day, it’s about supply and demand.” WTI traded up $1.09 or 1.43% to close at $77.58. Brent traded up $.91 or 1.11% to close at $82.53.