Oil declined for a second day, erasing an earlier advance of 0.6 percent. Oil for August delivery slid 65 cents, or 0.8 percent, to $78.56 a barrel at 11:09 a.m. on the New York Mercantile Exchange. Prices have fallen 24 percent this quarter, the biggest drop since the final three months of 2008. Brent crude for August settlement rose 23 cents to $91.24 on the London-based ICE Futures Europe exchange. Brent’s premium to West Texas Intermediate widened for the third straight day, rising to $12.68.