I own a 2004 Civic Coupe EX. I'm looking for better gas mileage and I wanted to know if it is possible to modify the engine's ECU so that it runs like an HX? I'm not sure if that is something a mechanic could do or if it requires buying/installing an aftermarket ECU.

 

The HX has a different engine and transmission, if I'm not mistaken.

 

ya different gearing in the tranny and different head i believe.
your best bet to get better milage is drive softer and coast longer..

 

yea, if you really want an HX just sell what you have and buy one... you should be able to do it virtually for free if you can find an HX for sale and a buyer for your EX

 

why would you want to convert, you won't notice a huge improvement in the gas mileage. if you want an HX just do a trade or sell your EX and get one