I just put a CX tranny in my LX civic (5 speed).
In 5th gear....
LX- 3k rpm= 74mph
CX- 3krpm= 89mph!!!!!!!!!!!!!!!!
not good for performance but good @ the gas pump!

 

believe it or not, you may not see an improvement in gas milage. although you are spinning the motor slower to acheive the same speeds, you may have a higher load because of the gearing...if you want to save gas, be easy on the pedal and shift early. on my vx engine, i got anywhere from 25-50 depending on my driving style. on my ls, i can get between 22-35.

 

Modified by CardDealer at 3:07 PM 11/16/2006

 

It also depends on the torque peak of the motor - where it's making power the easiest. If it's right below the peak, but high vacuum (low load/partial throttle), it's going to give you great milage. [Albeit a flat tq curve wouldn't follow that] That tranny will be putting you at 2.5k at 74mph, which is much farther out of it's torque range than I'd put it. There's a reason every car manual reminds you not to bog the motor.