I've had my 2002 MINI cooper S for about 2 years. Driving to and from work, 30 MPH average, hilly, curvy, 2 stops in 4 miles each way. Both with 93 Octane fuel. I also have a Dodge grand Caravan and a Chevy Avalanche. Thought this was interesting.
These are all on the same route over many miles.
MINI = 27 MPG average
Smart = 38 MPG average
Van = 17 MPG
Avalanche = 12 MPG
On interstate the MINI gets 37, van= 25, Avalanche= 19, haven't had the Smart on interstate yet.