I would suspect that a lot of the weight problem can be cured by tire
pressure.

I have a 98 Civic HX which has consistently gotten 51 - 54 miles per
gallon.
I keep the tires "well" inflated.  I don't need a tire pressure monitor
that some
cars have.  I just keep track of mile gas mileage.  If it gets down to
the 40s,
I know I have one or more tires down in pressure.

Undoubtedly.  Weight is a killer.  The 2000 Honda Insight had a max load
limit of 380lbs, much to the digust of two 200+ lb commuters who bought
one together to carpool to work.  They were getting almost half the
epa estimate mileage by exceeding the max load.

nb

I suspect the goodness of the new Civic isn't much of a surprise to
anyone monitoring this newsgroup.

The review did mention not meeting EPA mpg estimates. I used an Integra
for commuting as well as typical family chores. I found I consistently
exceeded EPA when commuting but failed to meet EPA when I put more
weight into the car. Was my experience typical?

Honda Civic is surprising
Anytime the price of gasoline rises significantly, many prospective car
buyers think maybe they should veer away from the big chug-a-luggers
and buy something that sips the increasingly precious fuel.
at http://www.washtimes.com/autoweekend/20060222-115219-9023r.htm