General Motors posted a 10 percent increase in June US sales Friday amid strong demand for its more fuel-efficient vehicles. \"The month caps a successful first half of 2011 for us in the US market,\" said Don Johnson, GM vice president for US sales. \"Our sales are up and we\'ve gained share profitably.\" GM\'s sales for the first six months of the year were up 16.8 percent at nearly 1.3 million vehicles after June sales rose to 215,358 units. GM said it continues to reduce its lower-margin sales to rental car companies even as it expands sales to commercial accounts which rose 31 percent in June in the 15th consecutive month of sales gains. Total fleet sales were down one percent while retail sales were up 16 percent. Passenger car sales rose 28 percent in June, led by the fuel-sipping Chevy Cruze. Crossover sport utility vehicle sales fell two percent while pickup truck sales were up five percent in June.