The New Yorker has a piece that puts the recent announcement about how Starbucks has created a new product line, dubbed Oleato, that puts olive oil in coffee, into the context of its development as a company, culinary influencer and cultural force.
The writer, Gideon Lewis-Kraus, as it happens, has a father-in-law who lives in Milan, where Oleato already is available. So he took him there to sample the new brew, and offers a critique.
I won't reprint the whole thing here, but suffice it to say that the phrase slick, oleaginous sediment is used in the review.
You can read it here. (And I recommend it.)