I recently spent 10 days with a Fiat 500c - fun car and great handling. (My review
is online here for those interested.)
I decided to look up the specs for the diesel version (not sold in the U.S.) as I was curious how fuel efficient it would be in diesel guise.
It uses 3.3 l/100 km (71 mpg) in highway driving with a 1.3-liter 95 hp motor that develops 200 Nm (147 pound-feet) of torque.
We probably won't see the diesel 500 and 500c here in the U.S. but 71 mpg is something that would make people forget about hybrids.