We have a '92 and a '95. A new O2 sensor can do wonders. The tricky thing about the VX is the tank is hard to fill to the same point every time if you are checking mileage that way. If you stop at the first click, there can be 2 more gallons squeezed in if you are patient. I made the term, "hyperfill" for getting it really full.
I always love to hear about high-mileage Civics. Gives me hope for a few hundred thousand more miles on mine.
Definitely do a standard tune up. It's easy and relatively cheap. Keep your foot out of the gas, and keep your tires inflated.
There is a fuel computer available that gives you instant feedback on our mpgs... that alone could net you the biggest fuel savings, barring any mechanical issues. It's called the mpguino.
This site is the closest thing to a VX owner's club that you'll find. Definitely read up and ask any questions if you think your car is doing something weird. Chances are, someone here knows how to read the tea leaves.
slogfilet - I'll take you up on your suggestion for tech help. I replaced the clutch on my '92 VX with a new clutch, pressure plate, throwout bearing kit last summer. I have only several thousand miles on the new clutch and I'm getting a squeaking sound from the throwout bearing, when the car is either in neutral or in gear, i.e., foot off the clutch. With my foot down, the sound goes away.
I can pull the slave cylinder lever back slightly and the sound goes away, so I know it's all about the throwout touching the pressure plate as it spins. But our other VX makes no such squeak, and it uses the same brand clutch parts.
I'm assuming I need to pull the tranny and do the clutch set again, claiming warranty on the parts. Would you agree? Have you heard of this type of noise?
Also, I know that the tire size is really particular on these cars and affects the mileage. The 165's are getting harder and harder to find. But the tire rack has them and they are sumitomos. Other than that I agree, do a tune up and use factory plugs wires, distributor and rotor and also check timing. These should fix your mileage a little.