I think you're using highway-driving only. The estimate for the latest Civic I could find (2012) is 67.3MPG UK (55.9MPG US) combined, using a British cycle. This is diesel, which has a higher energy density than gas, so the equivalent in gas would be 49MPG. But also note that european MPG measurement cycles are much more generous than US ones: the EPA measure would be much lower in the US.

All in all the Volt probably is almost the same as and possibly better than, the Civic in gas-only driving, despite the fact that it has to lug around an additional electric motor and battery.

Sorry, should have mentioned - it's a 2.2L diesel.