It's Ok to misspell any other word on this site except vtec. I you misspell tunner or milage no one seems to care.

I highly recommend everyone who is interested in their mileage keep a logbook. It is the only way to know if your changes are helping or not. This logbook page is from my '06 LX manual sedan. Now that the weather has warmed up a bit here in northern Illinois, my last tank averaged 36.5 MPG

 

the difference between models are all over..... the better milage civics usualy had lighter parts all over the car that was the main reason it got better milage.....

i know my old crx HF i had light weight parts all over it that added up to a lighter vehicle.
= better milage... its not just the motor or computer.... its not that easy.

IMO your geting about the best you can typicaly get unless you go nuts like that ugly @ss civic pictured earlier.LOL and thats way to ugly to be good on milage for a daily driver! ugly> milage gain.

 

I am ordering my CF hood/trunk with my next paycheck. I just got all my suspension parts in, waiting for my short throw that will be here on monday. CF hood and trunk should lighten me up a little bit, my spare tire is allready out, and the car is about as light as i can get it and still maintain some reason. I am really interested in the differences between the HF and the SOHC though. If anyone can tell me what makes it "tick" different that would be great. Maybe I could incorparate some of that into mine.

 

well all i know is that on like 84-86 or 7 cannt remember there HF versions used basicaly no power options, and the rear drums where aluminum over the cheap steel drums to save a few pounds. from what ive heard it was a few pounds all over... that added up. and the HFs had a upshift light to tell you to shift to get best milage..

the carbon fiber hood and trunk sounds like it may help alittle..... but unless your car is a track car then i would say most the weight reduction is just accessive...
like some people remove there power options off the car, and some people also scrap the factory sound deadening off the floors and such, along with carpet, trim panels and pretty much everything ya dont use...
BUT doing that will promote LOUDER interior noise, and look ugly interior. and if ya remove the seats well.... lets face it now one else can ride in your car.LOL

not worth another mile or 2 a gallon to me...


i have noticed one thing that of course since i added my stereo i have lost about 2-3mpg.... due to the weight added and the electrical strain on the alternator all the time.

simple test there is start your car up with everything turned off then turn your fan on FULL and you can hear and see the tach go up and down from the alternator engaging.....
so posibly keeping the fan on a slower speed could also help milage by puting a smaller strain on the motor.

there is so much that would could do but at the same time so much thats more practical.... hell im my car the heater is on FULL BLAST all winter long! i get my best milage when its warm enough to roll the windows down and just cruise with no fan on...

 

I was wondering about this too. I actually started rolling in neutral on this tank of gas, and that was around 5 gallons ago. I have an auto, but I have been careful. I live in central Arkansas and it's very hilly here. I have found that there are places on the interstate that are nothing but downhill. There are places where I can drop it into neutral and roll for up to 1.4 miles at around 70-75 mph at 1000rpms. I actually pass people while I am in neutral. That'sjust an amusing feeling to me. There's an offramp where I can drop it into neutral from 65mph cruise control and roll down the offramp and then up a coverleaf onto the bridge above the interstate, a distance of .3 miles. Doesn't sound like a lot, but you would be rolling at 45mph at around 2500 rpms otherwise. I do that every other day, so surely that counts for something. There are several other places where I do the same thing, like rolling to a stop at an intersection from 500 feet away. At the stop, shift back into drive and go. Of course, my efforts might be negated by the uphill parts of the drive... That's another downside of living in a hilly place. I try to coast as far as I can uphill, but in the end I still have to use some gas to get uphill.

Thus far, I'm looking at about 40mpg with combined highway and in-city driving in a 2000 LX.

 

If you do any coasting in neutral with an automatic tranny, plan on some expensive repairs in not too long a time. It also messes up the computer/injector settings which rely on vacuum/tranny oil pressure for the right settings. You should trade for a manual tranny Civic. The auto tranny is designed to drive the tranny from the inputshaft not the output end.

 

the hx motors get about 45mpg if there in tip top shape. my cx(d15b8) got between 39-40mpg.

 

well ive heard from alot of people that puting a automatic in nuetral can actualy hurt the tranny.... but i have no proof... i just dont try it in mine because a automatic tranny is expensive!

with a manual you know its disengaged. but a automatics main killer is heat.. in the fluid.
most the time i dont even put it in neutral and just hold the clutch down..... and let let off the clutch and keep rolling...
so i wont recomend doing it with a auto but a manual i do it all the time!

a manual is easy to descibe cause its just gearing.... but autos are a whole new world!

 

Ok you guys still are not getting the point I was trying to get across on this thread. What modifications can be done to the engine to increase MPG.
Weight modifications, putting it in neutral, or drive, or using the break vs not using the break, tune-ups those are all simple things. A lot of people are wanting to do the performance things like engine swaps, turbo's, I/H/E, and I wanted to see about the other side. What could be done to a civic engine to make it get better gas milage.
Changing the PW on the injectors? Is it possible to change the map for the MAF to run leaner with out risking pre-det or burning a hole in the piston. What about the idea of the ECU from an HX? There is a crazy amount of knowledge on this forum I was wondering if anyone out there knew more about actually changing the tune of the engine to get more MPG. If the HX gets 45mpg, how does it do it, besides the weight issue.

 

Your thread evolved, though, and that's cool too. (I'll probably quit with the neutral thing if it's harmful.)

We have covered some of the basics, though. Weight reduction is a big one. The I/H/E bolt ons add a little. I'm no expert, but I would think a turbo would actually decrease economy... (comments, please?)