Which type of whiskey is traditionally used in an Old Fashioned?

Bourbon is traditionally used in an Old Fashioned because it has a flavor profile that complements the drink's ingredients. The Old Fashioned consists of simple components: whiskey, sugar, bitters, and a twist of citrus, allowing the whiskey's characteristics to shine through.

Bourbon typically features a sweet, rich profile with notes of caramel and vanilla due to its corn base and aging in charred oak barrels. This sweetness and full-bodied flavor pair well with the sugar and bitters, creating a balanced cocktail. While variations of the Old Fashioned can utilize other types of whiskey, bourbon is the classic choice recognized in most bar settings and cocktail recipes.

In contrast, Scotch offers a smokier and more complex flavor, which may not blend as harmoniously with the other ingredients of an Old Fashioned. Irish whiskey tends to be lighter and smoother, lacking some of the sweetness that enhances the drink's flavor. Tennessee whiskey, while similar to bourbon, often has a different production process that includes charcoal filtering, which may alter the flavor profile enough to not align with the traditional essence of an Old Fashioned. Therefore, bourbon remains the quintessential whiskey for this classic cocktail.