Understanding Fuel Injection & Mpg Loss

[brtt485]

Hey All,

I am working on diagnosing a pretty substantial drop in MPG on my 2006 Silverado 1500 4x4 w/ the 5.3L. For 70,000 miles I never reset my AVG MPG calculator and I was running at 16.8 combined city and highway. At about 70,000 I noticed the AVG MPG start dropping so I reset it and over the past 10,000 miles I have been averaging 15.3 MPG.

 

Here is what has changed since about 60,000:

- Switched to synthetic blend oil

- Increased tire pressure to 39 psi up front and 38 psi in the rear (should help some)

- Ran some seafoam through the intake (thought it might help clean things up a bit)

 

Oil is changed on average every 4k miles, I run 87 octane, regularly change air filter. Based on the research I have done here the only things I can think of that could be causing this are the fuel injectors (dirty), throttle body (dirty), or the computer.

 

I dont know enough about how this engines fuel injection system works to get any further so I was hoping someone could chime in with some ideas but I would really like to understand how this engines FI system works.

 

Thanks!

[Nytemare]

You live in a cold weather climate and that along with the use of Ethanol in the gas will reduce the fuel economy. If you have an aftermarket fresh air intake remove and reinstall your OEM for the winter. Cold weather requires more fuel and warm less. Reset your AVG MPG calculator at each fill-up to get a more accurate fuel usage.

+1

[Jsdirt]

And I see that you live in the great liberal bastion of MA, brtt485, as do I ... You know how our state is run by folks who put the environment above all else? Well that way of thinking has made it's way to the pump too. MA I have found uses DOUBLE the amount of ethanol found in other states. You can tell almost immediately when you leave the gas station -- it feels like you left the e-brake on ... down on power, & mileage goes down the toilet.

 

The last time this happened, I threw my scan tool on the truck & was shocked to see an alcohol content of 19.6%!! I have a flex fuel 5.3 & have never even seen a E-85 pump, let alone put the stuff in my tank.

 

You can thank the great leaders of MA for your crappy mileage, & getting ripped off at the pump. Saving the world, one tank at a time ....

[redvett]

You live in a cold weather climate and that along with the use of Ethanol in the gas will reduce the fuel economy. If you have an aftermarket fresh air intake remove and reinstall your OEM for the winter. Cold weather requires more fuel and warm less. Reset your AVG MPG calculator at each fill-up to get a more accurate fuel usage.