Need help. Getting bad mileage on my civic

[GasSavers_Rikaro]

i changed the o2 sensor because of bad mileage but it didn't help. It's probably something else

[VetteOwner]

change your wires! thier prolly more important than the plugs themselfvs

[GasSavers_Rikaro]

ok. so i think i'll go for the spark plug wires. A quick question though, do i need 8mm or 10mm ones for better mileage? also would one or two disconnected spark plug wires lead me to get bad mileage? or it won't even start up at all?

thanks

[Gary Palmer]

If you replace the wires, get the 10mm, they will allow more current to flow. If you have one or more wires either loose or disconnected, it will significantly affect your mileage. How it runs and how much it affects you would depend on which wire or wires are loose, disconnected, crossed and so forth.

It will start and run, under some conditions. I have had two wires be crossed and the car idled ok, not great, but ok, but when I tried to drive it, it had really lousy power and took forever to get up to highway speed. It did run though, which surprised me.

[Raccoonjoe]

I've had several cars run with crossed plug wires before. (It makes a great practical joke....)

Also remember to take into account for your tire size. Your new tires are 1.9% bigger than the old ones, so your MPG formula would look like this (odometer*1.019)/gal. Basically, just take your odometer reading for a tank of gas, multiply it by 101.9% to get the actual reading......then divide by gallons used. PM me if you want/need this in automagical spreadsheet form....

[Weliin]

I was getting bad gas millage from my 98 civic (about 23mpg in the city) and I tossed in a bottle of gum out fuel injector cleaner and all was good again.

I now toss in a bottle every 3.5-5k miles. It seemed to help me.

[VetteOwner]

yea i ment plug wires. thier realtively cheap. i usualyl run seafoam every oil change. it does wonders...