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Unlike most people in the forum, I'm looking at ways to improve my fuel economy more than improve my performance. I was wondering if it was possible to swap the HX final drive gear (3.842 ratio) in for the EX final drive gear (4.412 ratio)? Since I do the majority of my driving between 65-80 mph, I figure this would drop my RPMs by around 500 in 5th gear. If this is possible, can you think of any damage that might come from making that sort of change?

 
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Well ummm the car does so well on gas anyways, and at a steady highway cruise it runs just enough gas through the motor to keep it running, I'm not seeing a few hundred RPMs making a significant difference. A fair number of people (myself included) are seeing high 30s-low 40s on the highway as it is.
In addition, you may find yourself wasting more gas than you save because you'll need to rev the living **** out of the car to get it to move, you'll have no passing power and the car generally won't stand a chance of getting out of its own way.
The middle ground LX/DX FD of 4.11 might be a possible option... but I really don't think its worth the effort. You'd be gaining maybe a MPG, and the final drive is a couple hundred bucks plus installation or time and effort depending on who does it. It would take so many miles to justify it, I don't see it being worthwhile at all.

 
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Thanks for the input. I took a look at my shop manual also and realized I'm never going to want to do all of the work it would take to remove the transmission just to replace the final drive. I'm also getting high 30s - low 40s on the MPG but always looking for ways to improve.

 
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drive slower... jk it would be way too much work man. I have an hx and i'm getting mid to low 40's. Not really worth it imo.