intall o2 sensor/ bad gas mileage

I have been getting bad gas mileage for awhile now and it seems that I'm not the only one experiencing the 200 to low 300 miles per full tank. I just want to know if anyone tried to replace the o2 sensors already, and if so how do I replace them myself? Thanks for any feedbacks.

fellow maxima driver

It could be your knock sensor. Check your ecu codes and then you'll know. The knock sensor wont make your check engine light come on but it will throw a code.

I get 230 miles on 3/4 of a tank about 21-22 miles per gallon in mixed city-highway driving. The best I've experienced was about 29 miles per gallon on a long distance all highway 75 MPH average trip. I think thats
average for the max. If someone is getting better please let me know how. Tire pressure is important 32-35 minimum.

do the ks, also check your fuel filter. i used to get a max of 325 miles per tank. i did that and swicthed to cheveron 92 and now im hitting 400 per tank!!!! thats some crazy stuf.