I changed my fuel filter yesterday. Been about 5k miles and have started noticing a slight decrease in mileage no matter how much i've been babying the gas pedal. Anyway, when I pulled the filter off, I noticed that it was maybe half full and not topped off like the last time I changed it. Does this mean I may have had air in the system that I needed to bleed out? Could air in the system cause a slight decrease in mileage or would a dirty filter have more of an affect on that? Just curious. I ran the tank low a few times, but it was never enough to kick on the low fuel light. Put the new filter on and blead the system. Starter right up as usual. Guess i'll just monitor it from here on in. Thanks in advance.

Ken R.

The Duramax uses a suction side fuel filter so it's normal for it to be partially full. See the following for more info.

Suction/Vacuum Side Fuel Filters (http://www.baldwinfilters.com/engineer/pdf/94-6r.pdf)

Some of us have added a lift pump (http://community.webshots.com/album/77018086bLHHHC) to slightly pressurize the fuel system and keep the filter(s) completely filled with fuel…

:)

Good info. Thanks.

Ken