Need more precise numbers to be viable. Did you fill up with exactly 10.00 gallons of gas in the car after driving 430 miles? When you're talking about that kind of MPG, the tenths count! 2 tenths of a gallon in either direction can put you anywhere from 42.16 to 43.88, a significant difference.

Is your Civic a VX? The new highway EPA on a '93 Civic VX is either 45 or 49. (with no clear indication of what the difference is between the two specs... gotta love unclear data) I'd give you the benefit of the doubt and call it 45... which means you're close, but still below EPA. Still not bad, though!

You should be able to see 50 mpg easily with that car, just takes a little dedication to the cause.