2004 pontiac aztek bad gas mileage

[Kelsey92504]

I have 2004 2wd aztek. About 3-4 months ago I changed the pcv valve, fuel filter, air filter, and cleaned the throttle body and mass air flow sensor. I haven't changed the plugs and wires yet. Its been about 2 years since changing the plugs and wires. I always fill the tank up because it used to last longer. After changing all the stuff I listed above, the gas mileage went from about 300 miles a tank, to almost 450 miles a tank. Since then it has dropped back down to the 300 miles a tank. Today I pulled the fuel filter of again to check and make sure it wasn't plugged and it was good. You could blow threw it like the new one. Would plugs and wires really cause the big of a drastic drop in mileage? Is there anything else to check, clean, or replace? Thanks to everyone.

 

[melsg5]

You have verified that with the engine running there is no leak at the fuel filter? have you rechecked that you installed the correct part number PCV ? did you use a brand name air filter? How many miles are on the plugs and wires? Do you have a check engine light on?