Diet Mountain Dew is a no-calorie Mountain Dew that was first introduced in 1988. It was formerly known as "Sugar-Free Mountain Dew" until 1986, when it was given its current name. In 2006 Diet Mountain Dew was reformulated with a new "Tuned Up Taste", using a blend of sucralose, aspartame, and acesulfame potassium as sweeteners. The previous formulation was sweetened exclusively with aspartame. In limited areas in the United States, Diet Mountain Dew has treated water instead of carbonated water as a fountain drink.