Caol Ila, long owned by Diageo (from back when it was DCL) and long used as fodder for blending because of its subdued peatiness and round, nutty undertones has in the last decade won more recognition as a single malt. The distillery itself, rebuilt in 1974 to crank out whisky for blending, has the largest capacity of any distillery on Islay. While considered to be milder in peat flavor than its contemporaries (Ardbeg, Lagavulin, and Laphroaig), its malted barley (from the maltings at Port Ellen) is the same as the 35ppm peated malt used by Lagavulin. Caol Ila’s quiet nature must be derived from some element of its process of distillation, some characteristic of its stills, or perhaps from the minerality of its water.
Caol Ila is a component in Bell’s, Johnnie Walker (especially in Double Black), and other Diageo blends. It’s interesting to note that Caol Ila switches to production of unpeated malt for part of the year (sometimes released as a single malt as well), which is also a component in Diageo’s blends. Caol Ila is shipped via tanker to the Scottish mainland, filled into ex-bourbon barrels, and aged in a Diageo warehouse. 95% of its production goes into blends.