OK so I have a 2001 honda civic Ex 4 door, my main concern as of right now is that my mpg is averaging from 22 to 24 mpg, (<250 miles per 10.5 gals) although reading online the averge is between 30-35 mpg.
I actually accelerate pretty slow, unless I hit 55-65 mph I don't hit more than 2.5 revs, my gas only went up by a little, 20 more miles, so it really didn't do much
I do drive in the city a lot going to school and such.

It seems like there is no fuel filter ,but with fuel pump, I have no idea with that,

Actually, this car also has the idle problem in summer, but in winter it also happens,
Becomes less, these days I use higher rank of oil, it does not idle any more. I know it will
Idle next summer, this happens every year. HONDA dealer also can not fix this idling problem.


Any suggestions for the two main problems ?
Thank you so much

. These tips should help improve your gas mileage:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-4.html#post293582

Be sure to replace the spark plugs (NGK only). Use SAE 5W-30 full-synthetic engine oil, changing oil and filter every 6,000 miles or 6 months, whichever comes first.

. Clean the Idle Air Control Valve, throttle plate, and throttle body:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-7.html#post1054149

Afterwards, replace the air filter.

Thank you so much for your prompt response!
For Honda civic 2001 EX, there is no fuel filter(need verification), only fuel pump, should I change that?
I just replace the spark plugs last year, it worked better just for two weeks, then it idled again.
Should I change air filter every 6,000 miles?
Should I use Chevron Techron fuel cleaner or shell brand to clean the gas tank? I did not do that for one year.

There's not a separate fuel filter for your Civic; instead, there's a fuel strainer. The fuel strainer resides in the fuel pump, which is located in the fuel tank.

Make sure you installed the same NGK plugs that came in your car. I would add Techron fuel injector cleaner to the gas every 5,000 miles. Change air filter every 30,000 miles or 24 months, whichever comes first.

Here are additional tips, to keep your Civic in top shape:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563.html#post219991