What motor should i go with for my 93 honda prelude?

H22A. But don't go with the Euro R, Type S, or S-Spec versions, just the regular old H22A. It has Intake Air Byp built into it's intake manifold, which opens up at higher rpms, as well as vtec, both are good for gas mileage at lower rpms and performance at higher rpms. Your stock transmission will also bolt right up to it, which would benefit gas mileage over the shorter geared H22A transmission.