[brucepick]

I think you'll have success if you address other areas.

MPGuino to see fuel consumption. And an aftermarket digital temp gauge so you can see that it warms up properly, and so you can build a grill block and observe that it doesn't run too warm. Needle gauges are nice but I like digital for engine temp.

Face it, the Prelude is made for sporty performance, especially the Si version. Probably is geared low for higher engine rpms and has wide tires, both of which will cost you mpg. When it's time for tires, get LRR ones, and get the narrowest that will fit your rims. Consider one size larger diameter tire than stock. Very likely it will clear OK, especially if you go narrower than stock. Compare with similar weight Accord of the same year to see how much tire is needed to support the car.

When you really get into it, consider a belly pan.