Hopefully Ronan gave the explanation for what is oxymoron in that car.
I copy/paste his answer : "Actually I've thought the same about the
towncar too in that in Europe anyway a "town car" sounds very similar to a "city car" which usually means something small like the Smart ForTwo or a Mini, not a full size saloon/sedan!"'. When I first landed in NY, JFK, 10 years ago, I was really impressed to see these 5+ meters long Lincols called towncar, so I thought : if everything is so huge in America, how a Limo would be...
The only ''Towncar'' Lincoln in Greece is the one of the Bishop, which hardly
moves in streets of Athens.
Anyway to me oxymoron is also the "Range Rover Sport", or the "Citröen ΑΧ GT"!!