brettnahmann

as said in the title,

1998 Civic EX
149k miles
5spd trans
been owner for 5 months

I gave it a fresh tuneup(plugs,wires,oil,tranny fluid, CAI, PCV valve, cap/rotor)
I regularly use 87 octane(lowest octane here in NY) but I recently switched to 89. Not having such a heavy foot, I avg around 27mpg; based off seeing between 22mpg and 29mpg.

Before the tuneup, I was rarely seeing above 25mpg. Id attain the extra ~2mpg to the PCV since it was infact busted. BUT I'd think for a civic mpgs would be in the 30s. I havent changed fuel injectors/o2 sensors or any treatment, but I've read seafoam could help very well, in the tank, crank, and brake booster. BUT I've also read that it could ruin some component vital to your engine since the grime it'd clean would break seals. I'm nothing but optimistic at this point since in this economy, I could use a few extra mpgs. ANOTHER NOTE, I'm not throwing any CEL's.

Any input/comments/suggeestions? BTW I'm new here and I normally frequent EJ8 squad.

THANKS IN ADVANCE!

98civdx

Have you checked the ignition timing? Is this all city or highway, or both?

I would just run some injector/fuel system cleaner in it, and leave it.


I know a few people who have used that seafoam crap, and never saw a gain at all.

mrprofits1

iTrader: (1)

i have done seafoam and i dont think it helps with mpg, but it does makes the car runs smoother.

fleabag

OP, my suggestion is you get a copy of the helms service manual and locate all the of the electrical grounds, then proceed to clean each and every one of them. Also make sure that the electrical ground wires aren't damaged because if you have a dirty ground, O2 sensor output/computer sensor input will be diminished and the car will run more rich than usual. Make sure your car is idling at stock RPM, possibly by buying yourself a Scangauge II or an Ultragauge which can read the OBD output from the ECU.

With one of those readers, you can get certain readings that may assist you such as coolant temp, RPM, o2 sensor output, MPG, GPH, etc. For example, I was able to, through the use of my scan gauge, figure out that my thermostat was opening and closing EXACTLY how it should be (opens at 190f, closes at 180f), that my car was idling at around 670rpm which is dead on stock, that my ignition timing was 14 degrees advance (12 +/- 2 degrees is stock), that occasionally my GPH (gallons per hour) would spike from .22 to .30 which lead me to investigate the car more closely and determine that I had a cracked exhaust manifold causing the o2 sensor output to occasionally be ignored by the computer, and that my fuel economy had improved measurably after replacing my PCV valve, long before I filled up the gas tank. The reason I prefer the scangauge II over the ultra gauge is that it will tell you if your car is ready to be smogged (if you clear OBD-II codes, your car has to run through its tests before it gives the ready indication, if it's not ready, it will automatically fail the smog test).

EsotericImage

iTrader: (8)

honda recommends BG 44k fuel system treatment

http://www.handa-accessories.com/civmaint00.html

Former User

This^

There's a diagram describing the procedure in the FAQs sticky.

redm3turbo

Not for nothing here, but theres a ton of things that affect gas mileage. One thing that made my car suffer a bit on the mpg is snow tires. I think Im getting around 29mpg with the snow tires, and during the nicer months I get in the 30's.

Tires will affect it, alot of other things will as well.

Also, another thing alot of people don't take into consideration is warm up/ cool down time. Right now in the winter, I let my car warm up a gd 5-10 mins before I go in the morning, and in the scorching summer, I let her "cool down" before driving that doesn't affect gas mpg per say, but it does burn it a little, throwing off your averages.

Lot of variables to say the least

brettnahmann

thanks for all your help! I never thought about the ignition timing but I'll look into that. As apposed to that fuel treatment, I'l try it out too.

And thank you for swaying me away from seafoam...looks like it can only do more bad than good.

EsotericImage

iTrader: (8)

ive used seafoam before.. but i read the directions..

not like half the kids out there trying to drive around on it while its in the combustion chambers blowing smoke down city streets.. i havent had any issues with it. I used it in the oil as well..

after i used it, i put in fresh oil for 20 miles, then changed that. no issues.


so the myth's that its bad is user related in my opinion.

Jimmy

iTrader: (5)

I actually have a tool that slowly ''drips'' sea-foam. Unplug the brake booster and run in thru there.. works well. I don't use it often, but it has never caused me any issues. my b18cR is extremely low miles.

Keep an eye on tire pressure too!