my car does a 180miles per full tank, i've changed everything u should think of to make it better, nothing worked, how do i know that my o2 sensors are fully functional?! i dont have any CEL

 

How about your thermostat? The temperature at which your car is running ( like too cold) will DECREASE your mileage.
BTW if there are no CELS then usually the o2 is good.

 

its always average, but my car drinks my radiator fluid weekly a little, i dont see any leaks and i've changed my thermostat switch twice cuz it stopped working suddnly

 

A lazy O2 won't throw a code. It's only when they get really bad that they will throw one. I say find one, switch it out and either it will work or you got one for when you do need it.

 

if its drinkin radiator fluid but u dont see any leaks u may have a blown head gasket

 

but my car doesnt overheat

 

and it doesnt have to do anything with my problem

 

Don't buy a cheap one, it's best to go OEM. I bought a Bosch O2 sensor and half a year later it's failing on me.

Check your tires, brakes for dragging, tune-up stuff?

 

i have oem o2 sensor, i have new brake pads and rotors too

 

so whats the problem?! i used a scanner for my car to check if my car is like factory civics, everything looks fine. i drive like a granny and i use 90 octane unleaded fuel. my auto tranny seems to slip on 2nd but it doesnt make that such thing

 

how do i know if my injectors are not just pouring fuel into the engine? i dont have smoke at all, its like my engine blows air from the exhaust, no colors or smoke at all