right now i'm getting around 19mpg mix driving, I've been easy on the gas though!!
4.8, running 20's with a 29" tall tire and 3.42's

 

I have 373 gears I am supposed to take it to the dealer this week, appearently the fuel composition need recalibrated hopefully that fixes it!

 

MY truck also has the eaton posi from the factory and MSd wires! God I hope dealership fixes it!

 

my flex fuel 5.3 with stock 20's was getting 22 yesterday on highway. i run on 93

 

Well they did the composition recalibration on my flex fuel truck today, still running 13.2 to 1 air fuel ratio nothing changed I wish I new how to fix this problem my gas mileage sucks and in full throttle it is 10.8 to 1, I am wondering if my gas has 10% ethonol from the gas station I wish I didn't have a flex fuel truck. Any suggestions?

 

I dont think the flex fuel has anything to do with the poor gas milage. And if the hyperjunk doesn't have a wideband o2 sensor directly in the exhaust then the a/f ratio you are seeing is wrong. And all fuel these days may have up to 10% ethanol. And will you please stop crying, maybe it's the way you drive?????????????

 

If you don't have anything nice to say don't say anything at all, well I drained the gas tank and started off fresh with shell 87 octane and some sea foam now the air fuel ratio is all over the place I drive like an old man d--k!

 

I thought I was getting bad gas at the gas station on base!

 

You have yet to answer... Does your handheld have a wideband to hook to the exhaust? and is it telling your PCM to run 13:1? I think thats the problem.

 

NO it is not running a wide band O2 sensor, and also all the tuning is out it is running the stock tuning all it is doing is observing. I was messing with it yesterday and I decided to disconnect all four O2's and then I cranked it up I figured it would stay in open loop but it didn't it warmed up and went to closed loop the air fuel ratio started at 12 to 1 and went to 13.2 to 1. I would of assumed that the airfuel ratio wouldn't have even registered due to the fact that the O2's were disconnected, this makes no sense to me.