Lately my gas mileage has gone from about 17.5 to 15. Cleaned and oiled my K and N, checked tire pressure, and ran a few thing of gas treatment the last couple of tanks. I have about 104000 miles on my 5.3. Any suggestions on my problem. only mods are the air filter and a flowmaster dumped

I think it might be the fuel filter but dont think it would cause this big of a decrease in less than a month. Is the filter just an in line canister or is it more difficult?

 

I believe it is an in line canister, and I also think there is another filter in your gas tank but I'm not very shure would have to ask someone with more knowledge. Sorry. . .

 

My truck has also dropped its MPG, But I think it's related to the cold weather in my area. So, I'm not too worried.

Jeff

 

It is an inline filter in front of the gas tank and there is also a "sock" on the pickup of the fuel pump, but unless you want to drop the tank......I have never had a problem with them. You could try your filter, but it could be a few other things along with the filter ie; spark plugs, clean the injectors, clean the TB. Just the little things combined can make a difference along with winter gas and such.

 

what about o2 sensors, at 100k i would think they MAY start crapping out, just a thought. They don't always trip SES lights till the last leg. I'd say PCV valve too.

 

Yeah it might be the o2, I here the average good lifespan on them are about 75K. If you got the dough than I would replace them.

 

When it is cold out some times it tries to die backing out of my parking spot. It knocks real bad for the first 2-3 minutes also but i have been told it is just the maf sensor and has done it since 40000 miles. maybe just plugs,wires and general 100k tune up. thanks yall

 

go get some spray type gm top engine cleaner from your dealer. Run it through your pcv line. This will clean out your intake and upper cylinders. Might be helpful if you've never used it before.

 

no i don't think so, i have replaced my fuel pump and have a new filter in place, k&n is clean, had a tune up at 105300, truck runs fine, no problems, no codes, i am at 114000 and i have droped from 18.4 to 15.1 on milage,
what ever it is we seam to have the same problem.

 

You might be experiencing the effects of winter gas...don't understand how it's supposed to help clean up emissions and the environment if you have to use twice as much of it.