A pioneering collaboration between Scotland's Harviestoun Brewery and Highland Park Distillery, conceived in 2007—the first ale ever matured in whisky barrels from a named distillery with traceable, numbered casks. Built on Harviestoun's award-winning Old Engine Oil porter, then aged six months in ex-Highland Park 16-year whisky casks. 'Ola Dubh' is Gaelic for 'Black Oil.' This is not a novelty barrel-aged beer—it's a structured, serious drinking experience where the worlds of Scottish brewing and single malt converge.