http://www.canadiandriver.com/news/021202-1.htm
They list it as being in a tie with the Nissan Sentra and Toyota Celica but I see they list the highway number as 5.9L/100km for the MINI and 6.0L/100km for the other two so it actually looks like a win by a nose to me for the Cooper.
Luckily for all three cars in the subcompact category, the ECHO has so much interior room that it is classified as compact, not subcompact.
Harry