Oil prices have fallen this month to their lowest point in years, but fuel costs haven’t fallen nearly as quickly. While West Texas Intermediate crude, a U.S. benchmark, has dropped 15 percent in the last month, the cheapest it has been since 2009, prices at the pump have slipped just 3 percent. A barrel of crude cost $42.61 Tuesday afternoon. The national average for a gallon of regular-grade gasoline is now $2.66, according to AAA, still much cheaper than last year but well above what a gallon cost last winter. The gulf owes to a handful of factors — more people drive in the summer, for example, and the blend of gasoline produced this time of year is costlier to make — but gas prices have also been pushed up by trouble at a refinery in Indiana, industry followers say. Machinery issues at BP’s refinery in Whiting, […]