[Christ]

The injectors used in D-series Civics are all basically 190cc or 240cc... that's about the only part that's going to make a difference in FE, really. Spray pattern might have an effect, but it's not going to be noticeable at the low power settings you're experiencing.



1988-'91 Civic Si/CRX Si Peak and Hold 240cc
1992-'95 Civic Saturated 240cc
1996-'00 Civic dx cx and lx Saturated 190cc
1996-'00 Civic ex/si Saturated 240cc

The problem could arise when someone puts 240cc injectors in the 190cc engines, but it's not likely that's the case here. Someone could have put 190cc injectors in your 240cc requirement, but that would only make the injector duty cycle increase to meet fuel requirements, and it wouldn't really even do that in your case, because you're never touching the max flow rate of the injectors.

In fact, I don't think you can really affect fuel economy too much by changing injectors at all, because the ECM just compensates for increased or decreased flow as much as it can. If it can't compensate to bring the mixture back into a reasonable margin, it will signal the CEL to come on, probably with an O2 sensor code.