I would definitely consider a d15z1 swap with VX/CX tranny.
I have a CX tranny and shift into 5th before I reach 45 to keep the rpms as low as possible. Also consider some lightweight 13" VX wheels or 13" jetta mags are light too. You could consider a Hot Air Intake as well...

He said 60-65% of the time. Losing your reading skillz?

how much negative affect does radio and fan(a/c off) operation have on FE?

welcome to the site and good luck pizza dude. I say if you're already in the high 40's with your current setup, not sure how much better it would get with a different tranny. You probably will see a gain due to the taller gears but you have to look at how much the tranny and installation will cost and how long would it take to pay for itself. If your increase is only a few miles better than what you get now, was it worth it? On the other hand, if you see far better gains, you can tell all the nay sayers, check out my MPGs now son.

I agree that for city driving swaping your tranny isn't going to help you alot, and might even hurt unless you switch to a matched engine that has more low end torque.
for stop and go driving reducing unsprung weight will help, 155/80 13" tires would help when your current tires go bald, civic vx, civic hx, or honda insight alloy rims are all light weight (flashy looking racer style rims are not alwas light weight) on a budget finding a set of stock CRX HF steel rims can still save a few pounds and alot of money (little over 12 pounds for the steel hf rims, compared to 10-11 pounds for the vx or insight rims), having electronics turned on does put a noticable load on the engine of the car, that is something that has been done on some cars, to turn off the field windings of the alternator while the engine is under a high load, the pay back might be a while, but things like Luxion LED tail lights can lower the electrical load, they are brighter so you are better seen, and they shouldn't ever burn out, so you don't have to worry as much about getting a ticket.

Good work Clencher.
I've done similar calcs for other ideas including buying a different car with better FE.

I finally decided, any mod or upgrade that costs more than lunch money takes too long for payback. For me, "lunch money" = whatever I'm willing to p**s away during the week out of my regular pocket money.

Dunno if I'd dare go 55 psi in 35 psi tires. Try 40 then 45, see how they look (random bulges in the sidewalls??). See how it handles. Go higher if you're comfortable with it.

I have 44 psi tires in a car spec'd for 32. Pumped past 45, the handling really changes. Smaller contact patch makes the steering get very light. No other way to describe it, ya gotta increase a bit at a time and see how it handles. I'm getting used to the lighter steering right now, probably will stay with the higher pressure.

welcome aboard. your getting darn good mileage already, if it ain't broke don't fix it!

mileage after AMSOIL
 

Well after ordering the oil, I wanted to get a accurate mpg reading. Now of coarse Ive been driving this civic for almost a year and wouldnt you know it the gauge cluster started to act up. I cleaned all connections, grounds and so on. I wanted to get a before and after reading. I did the oil change and tranny fluid change the other day. I filled up to the first click, then drove 61.3miles, went to the pump again (first click) and put in a whopping 1.084 gallons. :p

THATS 56.5 MILES PER GALLON
Amazing!

short fills ie. a couple gallons or less are pretty worthless for fe calculations!

https://www.gassavers.org/showthread....ght=short+fill

https://www.gassavers.org/showthread....ght=small+fill

https://www.gassavers.org/showthread.php?t=4016

soooo were the numbers i used for the tranny cost/benefit analysis any good?

The tranny swap
 

Yea Clencher your analysis did help. I prolly will keep the DX trans and just shift earlier in the RPM range. I will post up full tank mpg soon. I will go to the pump and top it off this time and see how far I can go. Also, will write down gallons and will turn slowley first 50 miles, so none goes on the road;)