Fuel Mileage

[4xbill]

I have a 2000 5.3L with AEM cold air intake and cat back system and I'm getting 16mpg around town. Not sure about highway though because I don't do much of that.

Oh yeah, I've also got a 6" suspension lift and 35" tires so I guess I'm lucky getting the mileage I get.

[ms14796]

I am having the same issues with my 05, 5.3L CrewCab (40,000 miles). Up until about 3 weeks ago I was getting 19+ mpg hwy and about 17 city. Then my wife (her truck) noticed the city mileage was tanking. Now it's about 14mpg. We took a trip into Fort Worth this weekend and my hwy mileage was a measley 15mpg. I ran 2 cans of seafoam into the fuel and changed out the AC Delco Iridiums for a new set. She had cleaned the K&N filter a week prior to the trip. On the return trip the mileage improved but only to about 16.5 mpg. I don't have a check engine light so I am thinking that the only thing that would interfere with the engine performance without giving me a CEL would be the MAF. I assume the way to clean it is to remove it from the air tube and spray it down with CRC MAF approved cleaner, is this right? About the knock sensor; doesn't that produce an error code when it goes bad?

[j cAT]

Originally Posted by ms14796

I am having the same issues with my 05, 5.3L CrewCab (40,000 miles). Up until about 3 weeks ago I was getting 19+ mpg hwy and about 17 city. Then my wife (her truck) noticed the city mileage was tanking. Now it's about 14mpg. We took a trip into Fort Worth this weekend and my hwy mileage was a measley 15mpg. I ran 2 cans of seafoam into the fuel and changed out the AC Delco Iridiums for a new set. She had cleaned the K&N filter a week prior to the trip. On the return trip the mileage improved but only to about 16.5 mpg. I don't have a check engine light so I am thinking that the only thing that would interfere with the engine performance without giving me a CEL would be the MAF. I assume the way to clean it is to remove it from the air tube and spray it down with CRC MAF approved cleaner, is this right? About the knock sensor; doesn't that produce an error code when it goes bad?

On both my vehicles i have k&n air filters....this winter after reading some comments about cleaning the maf and also internet searches on k&n air filter issues with the maf, it appears that proper drying of the filter before running the engine is necessary, or the maf will get coated with oil.....



after cleaning my maf i took a 250mi ride and as i got to the 100mi point i new it made a difference in mpg.

upon filing up tank after the trip i got 20+mpg....but also the throttle response was better....it's been 6mo. and the engine is still much better mpg and smooth power response..CRC cleaner.....it works and its safe..

[semisendiz]

I Recently Replaced Transfer Case Fluid And Both Frt. And Rr. Axle fluids As Well. I Will Let You Know On Mileage Variation Once I Filled Up 2 Or 3 Times...

[worstmechanic]

OK. Our engines all have an ECU (engine control unit). This control unit does what is called closed-loop control. That is, it uses feedback from the O2 sensors to make sure that the air/fuel ratio is where it is supposed to be.

So, how can oil from the K&N filter mess up fuel mileage. If the MAF reading is wrong, the engine will burn rich or lean, and the O2 sensors will see it. This should cause adjustments to be made to make the air/fuel correct again.