Diet Pepsi Changing Sweeteners Taste won't change, but articificial 'ace-K' should improve shelf life By Dustin Lushing, Newser Staff Posted Aug 31, 2012 3:20 PM CDT 24 comments Comments Diet Pepsi's sweetener formula will be tweaked as early as next year. (AP Photo/PepsiCo via PR Newswire) (Newser) – Diet Pepsi will feature a new formula as early as next year. The taste will remain the same, but the sweetener formula will be adjusted to prolong its shelf life, reports AP. The current sweetener, aspartame, loses its strength at a faster rate than the high-fructose corn syrup used in most regular sodas, and Pepsi is hunting for a mixture with more durability. A source tells AP that the new Diet Pepsi will use a blend of artificial sweeteners, including acesulfame potassium, known as ace-K. Mixing sweeteners produces a "synergistic effect" that extends their potency, explains a beverage expert. The move comes as Pepsi increases its advertising for its diet soda and seeks to regain market share. Diet Pepsi sold about half as much as Diet Coke last year. A spokesman for Coke says its diet soda, which uses only aspartame, is not slated for any changes.