How can a new fuel filter increase your fuel milage? I have replaced mine 3 times in 26,000 miles and i havent ever noticed a slight increase in milage. I keep a clean air filter installed. I get around 12mph local and 14 mph on trips.... My truck is 3500 dually 4x4 auto 4 door With 265 tires on it.

It doesn't increase mileage if you are changing it regularly.

A fuel filter can't increase mileage. It only filters the fuel. A Duramax uses a certain amount of fuel to accomplish whatever its doing at the time. A dirty filter will restrict fuel flow and eventually lower the delivery rate to something less than needed for the power requested. But its still getting the same mileage as its not dependent on fuel flow thru a filter. If it were...we'd just install huge filters and lines and expect better mileage.

I have been told by a few people and i thought i read on here some where in one of the fuel milage threads that if your filter was dirty it would reduce fuel milage. I couldnt believe that would cause bad fuel milage but it could reduce power for the lack of fuel flow.. I am a auto mechanic / body repair man and i couldnt figure out how they came up with that. .

I have been told by a few people and i thought i read on here some where in one of the fuel milage threads that if your filter was dirty it would reduce fuel milage. I couldnt believe that would cause bad fuel milage but it could reduce power for the lack of fuel flow.. I am a auto mechanic / body repair man and i couldnt figure out how they came up with that. .

From my experiences, I have found that your quote "but it could reduce power for the lack of fuel flow" is very true... in that once the Dmax finds that a lack of fuel flow has occurred, ie: dirty filter, gelled and/or very cold temps, as in my case, has occurred, then the truck won't run past 2000 rpm, and basically limps all the way, kind of, heck very.... ANNOYING, but for the the most part just says.... I NEED A NEW FUEL FILTER.... I try to change my filter before the "cold" season arrives, which coincides with maybe 10000 miles in between filter changes....

I keep a clean air filter installed. I get around 12mph local and 14 mph on trips.... My truck is 3500 dually 4x4 auto 4 door With 265 tires on it.[/quote]

I seem to have the same truck as you.... however depending on how DEEPLY I use my right foot, depends on how my fuel mileage suffers... I've just purchased EFI Live thru SoCal Diesel, and hope to increase my fuel mileage, which currently according to the DIC, is around 17.0 MPG, however hand calc'd seems to show around 16.0... oh well, as I've stated before, my right foot, although now a little limp, seems to get frustrated at times and get a little heavy.... I hoping with the EFI tune, it'll get me close to 18.0 MPG calculated.. yes I know it'll have to "dumbed down", with less power, but heck all I want is better economy....

If your getting fairly clean fuel a filter should last 15,000 miles.When I had a 2002 with the single pleat filter I ran them 15,000 miles and cut them open to find they were only 1/3 used up.The dual pleat filters in use now will not go as far as the single pleat.The guys replacing fuel filters at 10,000 miles must be getting real dirty fuel.I carry a spare,never know when it will be my turn!