97 Civic coupe

I have a 97 ex coupe that gets only 18 mpg on a good day. I'm not a lead foot and maintain my car well. I've recently replaced the plugs, fuel filter, exhaust manifold (cracked), and had an oil change. My air filter is fine. Check engine light is not on. Anyone having this problem too? Or is it just the fact that it's 13 years old with 204,000 miles? Still runs great though so I have no idea.
Thanks in advance!

Benny88

when u say air filter, do u mean stock filter? if so i cant help then
but if short ram or cold air intake, ive heard that if u dont reset ur ecu then there is problems like urs where your not getting the mileage u would want..

but yeah if its stock, sorry dont know whats happening!

civicpapi

How is it running? Ex's never did get great gas mileage (dx's much better). I average maybe 25 in mixed driving even when new.

18 sounds low, is that just city and stop and go?

make sure you are doing the gas mileage right, make sure you fill up the tank and reset the odometer, next time you go back to the gas station and write down the mileage and then look at the gas pump and see how much gas was pumped to fill it up.

Divide the odometer's number by the reading on the gas pump and that equals your gas mileage.

Example 255 miles driven divided by say 9.7 gallons of gas equals 26.28 miles per gallon.

97 Civic coupe

I do have just stock air filter. Everything is stock. I'm calculating it exactly how you said. It wouldn't be a big deal except when I got the car a year ago it was getting 23-26 usually. Then it went to about 20... then 18... it's gotten as low as 16. Civic with 127hp should be getting much more than 16mpg! It is all city driving but my driving style hasn't changed since the mileage changed. Car runs like new... people who have driven my car are in shock at how well it drives. Engine in great condition (at least it appears so... but with 18mpg i could be wrong)

dnice78

The worst I've gotten (averaged) in my EX is 26, usually above or below 30... depending on tha foot

civicpapi

Have you done the oxyegen sensors, that might help. Age can be an issue as well, 16 is low.

mcote

Brake caliper sticking and causing drag. You'ld smell it or feel a slight shimmy as rotor gets hot.??

Nosepicker

Make sure you're using the right viscosity. I went from 10w-30 to 5w-30 and my mileage went up.

97 Civic coupe

I always get my oil changed at the Honda dealership. I'm assuming they would use the correct oil.

gearbox

iTrader: (95)

never assume ive seen great shops use the wrong oil, fill too much, or forget to change the filter. honda dealers are even worse. in some places they just drive your car around the block and park it and say youre done. here are some common things that would cause bad mileage that you can check.

-worn oxygen sensors (even tho they last upto 100k miles, they start to lose efficiency in as little as 20k miles and continue to get worse over time).

-unevenly worn tires or underinflated tires (honda recommends 30psi)

-alignment is out of spec (how straight the tires point)

-driving style (if you mash the gas or go above 3k rpms alot or drive in a hilly area, mileage will suffer)

-environment (gas mileage is much worse at sea level due to more oxygen, and gas mileage is much worse in cold weather for the same reason). more oxygen = more fuel dumped in by the ecu.

-loose gas cap or faulty evap system can cause much of your fuel to evaporate

-higher than normal idle can waste gas (should be around 700rpms)

-worn spark plugs wires and incorrect ignition timing

-sludge and deposits in the engine (try a treatment of auto-rx.com in the oil)

-clogged fuel injectors can cause a poor spray pattern (more of a squirt instead of vapor) which wastes alot of gas. try lubecontrol.com gas additive

-certain tires are more aggressive than others and can have higher rolling resistance, causing worse mileage. some hybrid vehicles get a 10mpg boost just by using low rolling resistance tires that come stock.

it sounds to me like maybe the engine is just getting old and needs some cleaning to work more efficiently. i bet with the auto-rx and then the lubecontrol products in oil and gas, your mileage will go up significantly. even on my relatively new and clean motor, i got an extra 4mpg on the highway using the additives. i have gotten 15 mpg in my 2002 civic before just based on driving style so i know its possible to go that low.

Nosepicker

Man, this site would be nothing without Gearbox.

to Gearbox.

97 Civic coupe

I actually did try auto-rx and so far my mileage went up to 23mpg. Lot better than before. It's only been about 500 miles so hopefully it'll go up even more. Think I'll replace the spark plug wires too. One is a funky color and feels different than the rest.

MelJ

Word. I agree with gearbox. As for spark plugs:
http://www.aa1car.com/library/reading_spark_plugs.jpg
It's a great picture to tell you how the engine is doing.