My 2005 honda civic used to get about 33 mpg but lately its only been getting about 26 mpg,The car has 50k on it, I have no check engine lights or anything else and the engine runs smooth was wondering if anyone knows what could be the problem Thanks Mark

 

Do a tuneup, check your tires

 

filter, spark plugs, tires, rotation, balance, tire pressure.

also, where you like driving in the highway and then in shitty traffic? cause that will do it as well.

also, Lucas fuel cleaner or whatever its called.

 

is your car a manual or auto?

I have an 05 ex model thats a 5 speed and ive been getting 33mpg lately but during the summer for some reason i always got 38mpg and got 41 a few times. No idea why its this bad during the winter?.... I have an ebay cai with a k&n filter on the end

 

Where do you live? Colder winter temperatures and conditions can have an effect on gas mileage.

 

my car gets 30 mpg consistently. it's redonculous. my tire pressure is good. 2004 with 80k but no tune up yet. hmmm....

arnt we suppose to change spark plugs at 115k or 125k?

 

The owner's manual suggests it at 110,000 miles. Many people do it more frequently.
https://honda-tech.com/forums/honda-civic-2001-2005-78/faq-maintenance-schedules-2389234/

 

It's commonly done when the timing belt and water pump are changed right before 110K.

Double and triple check your tire pressure. And that small of a difference could be explained by a combination of tire pressure and driving habits. I usually return low 30's, but if I lead-foot it around town for a full tank, I can get 26.

 

hmm.... so the lucas injector cleaner can cause the mpg to go down? well, if thats true then my mpg has drastically changed.its been 4 consecutive tanks that my mpg has been lower than average.

 

i live in tennessee. I guess im lucky since ive never seen my mpg go below 30 yet. I need to change the oil but you guys think having a cold air intake on the car during winter/cold conditions would hurt my mpg over having the stock intake filter on the car?

 

I seriously doubt it. Colder air generally results in better mileage, as colder gasses are denser. More oxygen per given volume.

 

oh really? Then explain why I goto the same exact gas station at the same exact pump week after week. NO mods or anything done differently in driving to or from work.
My MPG dropped 2-6MPG after winter and cold temps hit.
Colder air is denser meaning it takes more fuel to burn efficiently.
Winter gas is formulated to stand up to colder temps meaning that a bit more of it has to be burned to do so efficiently.

In the summer I averaged 36-38mpg depending on how heavy my foot was. This time of year (Winter) I'm getting 32-34mpg again depending on how heavy my foot is.

 

I think you may have answered your own question right here. I've never heard that before, but if that's true, that's most likely the reason. All I was talking about was basic chemistry.

 

how to find out.how many gallon of gas i can get?

 

How long have you owned the car?

The most important factor in fuel economy is the driver. Have you changed your driving habits or local routines lately? If you're getting 26-33mpg on average, it would seem that you do a lot of stop & go city-type driving.

If you live in an area with colder winter temperatures, a drop in mileage is normal - especially if you make a lot of short trips. The engine is designed to run rich and idle fast on cold starts to warm the engine faster in cold ambient temps. Couple this with longer warm-up times and the common winter practice of allowing the car to sit and idle for warm-up or to retain heat, and it can put a significant dent in your mileage. Winter fuel blends also have a higher vapor pressure and tend to evaporate more quickly, although you don't have a Check Engine Light on so you don't likely have any Evap system leaks.