I bought a 2004 Civic EX coupe 5spd with 19,XXX miles approx 4 weeks ago. On my first three tanks I got 37mpg, 38mpg, 36mpg, now all of a sudden I an getting around 26mpg the last 3 tanks. My driving style has not changed at all--I even drive slower on the highway to see if it would go up. Anyone have any ideas what caused this all of a sudden? I fill up at the same Chevron everytime using 87 octane. Im driving to the exact same places and my tire pressure is fine. This is really crappy for a car only 2 years old.

Dave

 

check your air filter, it might need to be replaced. extremely hot and humid days can also hurt, but i don't think it would hurt it that badly.

 

Chevron BAH.. use Shell Gas for best mileage.

Anywho..

maybe your fuel system needs to be treated.. buy a bottle of Marvel Mystery Oil (walmart) or GumOut Fuel Injector Cleaner and run that through a tank of 87 or 89. And also use a K&N drop in if necessary.

 

Id run Tire pressure at 33 all around.

Im running shell 87 all the time. I use MMO once a month and I run Royal Purple Synthetic Oil ..

almost 20k miles huh check your plugs too.. i just changed mine (bosch 2pt platinum)

 

My oil was recently changed, the air filter is clean, 32psi all around--will be running some injector cleaner in the next few days also. Any other ideas that may work?

Dave

 

The AC will hurt your MPG too

Since when is Shell the best gas? I thought gas was gas...

 

AC will kill your gas milage!

if you didnt need your AC on when ya first bought the car and just now needing the AC im judging the AC is just killen the milage....
thats my EXs big gas killer
for instance.... i did a road trip when i got my rims.... on the way thier NO AC.. was cool enough out all the way 38MPG....
and on the way home it got hot 26 or 28mpg with the AC.
only difference was 4extra wheels in the car and the AC was on the whole time.

but what can ya do... ya need that AC

 

No A/C for me---Im in Alaska and may only use it once or twice in the summer. I guess my defrost automatically turns the A/C on even though it doesnt light up the button. My owners manual says even after you switch if off defrost to a different setting the A/C will remain on without the light---how stupid is that

Dave

 

hell i didnt know that!

my light always stays lit until i turn it off after i select defrost. but im always quick to turn it off when i dont need it.
if ya dont think ya need the AC you can always unplug the compressor see if that makes a difference.

 

it does that so it won't fog up the window i believe, all new hondas do it