Hey guys im seeing if anyone is having same issues im having. I got a 92 cx hatch with a JDM D15B im getting not so good gas mileage out of it. I do mostly highway driving and it does about 18 MPG i got about 195 miles out of one tank any suggestions to fix this will be great. My specs are D15B with aftermarket wheels 15’s on it. Got a JDM transmission on it shorter gears then the USDM version.

 

. How does the fuel line under the car look? Start the car and let it idle a few minutes. Then look under the car looking for gas leaks. Had that happen on my civic. About $150 to fix.
Check the fuel pressure regulator, does the oil smell like gas?

 

What ECU are you using ? The CX comes with smaller/lighter wheels than your 15" ones... the larger/heavier wheels will contribute in reducing your fuel economy.