The Macallan is well know for their good vintages and whisky's for more then 180 years. The Macallan became quite famous with their use of sherry casks such as Oloroso, Amontilado, Fino, Manzanilla etc.
The fact that you had a distinct oily body is a direct result of their small stills they use for their new make spirit. You need a very big and robust spirit to compete with first fill Oloroso sherry casks. Another thing is they have one of the smallest cuts I've ever seen before.
The apricot you taste can be traced back from the distilate aswell, the distilate from the Macallan seems to be quite fruity, oily, malty and above all nutty. Well when such spirit has an interaction with the sherry wood it can be resulted in wood spices, toffee/vanilla/chocolate, dried fruits, fruity etc etc. The strong apricotflavor is a direct result from the cask, the fruityness from the spirit slowly merged with the ex sherry cask and finally became an apricot flavor(in very simple words).
It's true that apricot flavors can be detect in the 18yo, lots of other flavors can be detect aswell. It's not uncommon that you taste dried raisins or perhaps tutti frutti. Depending on the situation such as straight from the marrying cask or straight from the bottle, the flavors can vary in an 18yo. If you dare to dilute your Macallan to say 20% abv, you'll notice a scala of aromas and flavors wich will give you quite interesting data.
I did had some apricot before in a Macallan and it wasn't an 18yo but a 15yo vintage from The Macallan. Odd? No, it's quite common if you use a sherry cask with the right type of spirit.
I hope that this contribution helps a little for you Patrick.