Bourbon or rye: the Old Fashioned, Manhattan, Sour and Boulevardier in each

Under the US federal standards, 27 CFR 5.143, bourbon is whisky from a mash of at least 51% corn, and rye whisky is the same with at least 51% rye. The rest is shared. Both are distilled at no more than 80% ABV, go into charred new oak barrels at no more than 62.5%, and are bottled at 40% or more, and nothing may be added to bourbon for colour or flavour. Neither has a minimum age in American law; straight on the label means two years or more in that new oak. Any whisky sold in Britain needs three years in wood, so every bourbon and rye on a UK shelf has had at least that.

The rest of the mash is the distiller’s choice. A bourbon can carry a fair share of rye, and a rye can be only just over half rye, so the two styles meet in the middle: a high-rye bourbon and a low-rye rye can taste close. The bourbon and rye whiskey pages set out the label terms, and what is whisky covers the rules for every style.

Corn usually gets the credit for bourbon’s roundness, but the barrel does as much. A new charred barrel gives up vanilla, caramel and colour fast, and bourbon and rye both get one, so the oak alone cannot separate them. What the grain adds on top is texture and spice: corn reads soft and full in the mouth, rye dry and peppery, with a bite at the finish.

The difference shows most when the whiskey has sweet company. Sweet vermouth, sugar syrup and liqueurs all add sugar. Rye’s pepper keeps them in check, so the bitters and the vermouth stay distinct. Bourbon meets the sugar halfway and gives a softer, fuller glass that suits a first-timer and forgives a modest vermouth.

Neither is the correct one. The IBA, whose specifications bartenders work from, allows either whiskey in the Old Fashioned and the Boulevardier, names rye for the Manhattan and bourbon for the Whiskey Sour, and gives rye or bourbon for the New York Sour. Our pages follow the same lines, and most of the rye recipes on our pages say bourbon will do, with a rounder result.

Our Old Fashioned follows the IBA: 45ml of whiskey, a sugar cube soaked with two dashes of Angostura and a few dashes of water, muddled until the sugar dissolves, then ice and a stir in a rocks glass. With nothing to hide behind, the whiskey is most of what you taste.

Bourbon makes the version most people picture, its vanilla and caramel sitting easily with the sugar. Rye makes a drier, sharper one, with the bitters more audible. Use a whiskey you would happily drink neat, since a harsh one is still harsh with sugar in it. Keep the sugar the same when you switch, and taste before you change anything else.

Its New Orleans relation shows how old the swap is. The IBA’s Sazerac is cognac with Peychaud’s bitters and an absinthe rinse, and the IBA notes that rye took cognac’s place after the American Civil War, when cognac became hard to obtain. Our page carries both: the IBA’s cognac drink and a rye version at 60ml. The Vieux Carré splits the difference with 30ml each of rye and cognac.

The IBA gives the Manhattan as 50ml of rye, 20ml of sweet red vermouth and a dash of Angostura, stirred and strained into a chilled cocktail glass with a cherry, and ours is the same. At five parts whiskey to two of vermouth, the vermouth is over a quarter of the drink. Rye’s dryness suits that: the spice cuts the vermouth’s sweetness, and the bitters stay clear.

Bourbon makes a rounder Manhattan, softer at the edges, and it is a common bar request rather than a mistake. The vermouth matters more than the choice of whiskey. It is wine, and an open bottle kept warm for a month flattens the drink whichever whiskey is in it; vermouth explained covers how long it keeps.

The same frame takes other whiskies. Scotch makes the Rob Roy, 60ml to 30ml of sweet vermouth with two dashes of Angostura, and equal parts of Scotch and vermouth with 7.5ml of Bénédictine make a Bobby Burns. Irish whiskey makes The Emerald, with orange bitters, and the Tipperary, with green Chartreuse. Rye with dry vermouth, maraschino and Averna is a Brooklyn, and rye with Averna in place of vermouth is a Black Manhattan.

The IBA’s Whiskey Sour names bourbon: 45ml, with 25ml of fresh lemon juice and 20ml of sugar syrup, shaken hard, and a few drops of egg white if you want them. Ours matches it and takes 15ml of egg white, dry shaken first, when a foam is wanted. Bourbon’s vanilla meets the syrup halfway, so the drink tastes round, with the lemon a step ahead.

Rye pushes against the lemon instead, and the whiskey stays in front of the sugar. The rye sour on our pages is the New York Sour, the IBA’s specification of 60ml of rye or bourbon, 30ml of lemon, 22.5ml of syrup and a few drops of egg white, with 15ml of dry red wine floated on top. Bourbon under the wine gives a softer drink; rye keeps pace with the wine’s tannin.

The same sour frame runs through the bourbon pages. Honey syrup in place of sugar makes a Gold Rush, lemon wedges and mint make a Whiskey Smash, and equal parts of bourbon, Aperol, Amaro Nonino and lemon make a Paper Plane. Shake anything with citrus in it; shaken or stirred gives the reason.

A Negroni with bourbon in place of gin already has a name. The IBA’s Boulevardier takes 45ml of bourbon or rye, 30ml of Campari and 30ml of sweet red vermouth, stirred and strained into a chilled cocktail glass; ours keeps the measures and serves it over fresh ice in a rocks glass. With bourbon it is rich, with vanilla under the bitter orange. With rye it is drier and sharper.

Keep the rye, swap in dry vermouth for the sweet, and the drink becomes an Old Pal: 45ml of rye with 22.5ml each of Campari and dry vermouth, a leaner glass. Its history, and the rest of the Negroni family, are in Martini, Negroni and the gin and vermouth drinks.

The Boulevardier carries the most vermouth of the four classics. At 30ml it is nearly a third of the glass, so a fresh, rich bottle matters more here than which whiskey goes in.

Tennessee whiskey meets the bourbon rules and adds one step. Tennessee law since 2013, by Wikipedia’s account, requires it to be made in the state from a mash of at least 51% corn, filtered through maple charcoal before it goes into the barrel, and aged in new charred oak. Jack Daniel’s gives its own mash as 80% corn, 12% barley and 8% rye. In a cocktail it behaves like a soft bourbon and can stand in for one.

Our Tennessee whiskey recipes are long drinks such as the Lynchburg Lemonade, not stirred ones, but any of the bourbon specifications here will take it. Whisky highballs covers it with cola.

Pour the other whiskey at the same measure and leave the rest of the recipe alone the first time. If a rye Manhattan tastes too sharp, try bourbon before you add vermouth. If a bourbon sour tastes flat, try rye before you cut the syrup. How to balance a cocktail explains why a small change in sweetness shows so clearly.

A few drinks are written for one whiskey and are worth keeping that way. The Mint Julep is bourbon’s: 60ml over crushed ice with mint and powdered sugar in a julep cup, where the corn and the mint sit together. The Brooklyn and the Old Pal are rye’s, and the rye page says so. Stirred drinks go through a mixing glass over plenty of ice. What the strength and age on either bottle mean is in how to read a whisky label.

The Old Fashioned, Manhattan, Whiskey Sour, Boulevardier, New York Sour and Sazerac specifications are the IBA’s, checked on 12 October 2026. Bourbon and rye are defined in 27 CFR 5.143, as amended in December 2024 and read the same day. The British three-year rule is in the retained Regulation (EC) 110/2008. The Tennessee rule is Tennessee Code 57-2-106, and the mash figures are Jack Daniel’s own.