My mpg recently dropped from 28 and change to 25 and change. No change in driving habits.

I was thinking PCV (although that has been replaced recently) or OXS ( This is original but I am not getting any warning lights).

Just looking for ideas of what it could be at this point.

Thanks,
Scott

 

Check your tire pressure, and spark plugs and possibly the ignition coil.

I use to average 22mpg and I realized I had a bad ignition coil and after swapping it i had 26mpg.

 

Cold weather will also reduce milage.

So will leaky fuel injectors (do a leak-down test), a bad fuel pressure regulator, plugged air and fuel filters, bad plugs and wires, etc.

Check your repair manual for details.

 

Is it time for an oil change? That might help, along with all the above suggestions. Later

 

The O2 sensor can get slow and lazy and affect mileage. As long as the ECU sees 'some' activity from it, you won't set a code. Get the sensor tested first before you replace it. FWIW, I had poor luck with the generic (Bosch) replacement sensor on my '90 Si. I ended up buying the OEM sensor.

As mentioned, cold temps, tire pressure, state of tune, can decrease fuel mileage also.

 

I had a similar issue and it turned out the spark plug garments were leaking oil in the plug chamber, and down to the plugs.