I know that owning a */C engine I should not be complaining about this too much, however mine has been REALLY bad lately. I do alot of city driving and I usally manage somewhere around 16 ( kinda heavy footed from time to time). The other day I took it into the shop to do the brakes and while I was there, replaced the fuel filter. Now call me stupid but I expected that this would either increase or maintain my fuel milage. However it has done the exact opposite. We have gone through almost a full tank of 93 oct. since the filter replacment and right now it is barely hitting 14 mpg!
How is this possible and what should I look at replacing to fix this. The car just hit 60k miles the other day. From what I can tell it still had the orignall fuel filter on it, and looks like the orignall plugs and wires. This means it most likely still has the originall O2 sensor has well. I plan on replacing all of these fairly soon. What else is there that I should look at as the cuase for this? what if any improvement can I expect from replacing those that I listed?

Change the o2. I bet that'* a contributer to the bad MPG'*.

dont use a bosch either, get a OEM from the dealer or pay half the dealer price at GMPD.



I'd also do a full tuneup, plugs wires, air filter.....



Not sure if you are close to anyone with a OBDII scan tool, you may have another sensor making it run too lean or too rich. I'd replace the plugs, wires, and o2 first before anything else though. this has always gained me a couple MPG with every car I've owned

I have a code reader. It is not putting up any codes.

Would AC Delco carry the o2 sensor? I can get AC Delco parts really cheap, so hopefully they carry it.

The air filter was just replaced about a month ago with an Air hog ( Read siggy)