Its partly a question of power. The hybrid Camry gets 200% city & 30% highway better gas mileage. Its a larger car than the Civic, seating 4 larger men comfortably. I'm the smallest at 5'-9" & about 200#. The hybrid real world numbers are double in the city & 1/3 again on the highway compared to the EPA numbers for the 4cyl. model. This improvement comes while still having a net horsepower about halfway between the I4 & the V6 models.

The Civic hybrid gets about 50% better mileage in the city. The current EPA numbers are 36/45 gas only/hybrid.

What engine & vehicle weight does his Civic have? Is it the CVCC? The Camry weighs in at 3680#.

A better comparison is the Toyota Prius. I know two families with three between them that get 50-60mpg. It will seat four & has some cargo room behind the back seat.