The operator of the biggest U.S. fuel pipeline system said on Thursday demand to transport gasoline to the country’s populous northeast is the weakest in six years, the latest symptom of a global oil market grappling with oversupply. Summer is typically when gasoline demand peaks in the world’s biggest oil consuming country as motorists hit the road for vacation, and keeping their gas tanks full strains the capacity of U.S. refiners and pipelines. This year, so much fuel is stored in tanks in the Northeast that Colonial Pipeline Co [COLPI.UL] said in a notice to customers that demand from refiners and fuel traders to bring gasoline through its pipeline to the region from refining hubs in the South was the worst in six years. For the first time since 2011, demand for the pipeline was below capacity for a five-day period starting early next week, Colonial said on Thursday. […]