PepsiCo Inc. will start selling Diet Pepsi without aspartame later this year, one of the biggest changes to the beverage in decades, after a consumer backlash against the artificial sweetener crushed sales. The company will replace aspartame with a blend of sucralose and acesulfame potassium in Diet Pepsi, Caffeine Free Diet Pepsi and Wild Cherry Diet Pepsi sold in the U.S. beginning in August. The move follows a 5.2 percent decline in Diet Pepsi’s sales volume last year, according to Beverage-Digest. Sales of Coca-Cola’s Diet Coke, which also uses aspartame, dropped 6.6 percent.