I finally got my $20 obd2-USB interface from hong kong. It plugs into my laptop and I get get real time data from my truck.

I have been playing with it etc.

One of the software I have been using a software that does mpg.

http://www.scantool.net/touchscan.html

While on a flat highway doing 65 MPH I get 15mpg. I know it's accurate because on my last full tank I got 13.5 mixed city and highway.

When I first got the truck I wa getting 17.5 with the worse driving habbits.

I don't think the winter gas would drop my mpg by 4mpg.

I did have an issue after I got my truck the timing chain skipped a tooth and it ran really bad for a while. Could this have fouled the plugs, cats, o2 sensors?

I have replaced, air filter, fuel filter, cleaned maf, cleaned throttle body, sea foam, reset the computer.

I have a slight miss at idle, no CEL, and runs strong. I have a 2004 Screw fx4 with 80k on it.

Bank 1 sensor 1 & 2 cycles between .1v-.6v

Bank 2 sensor 1&2 .7v But at 1500 rpm sensor 2 bank 2 goes between .4v-.7v

Bank 2 sensor 1 stays at .65v-.7v at 1500 rpm

And the long term fuel trim is 0.78% lean.

 

I can tell you, I have cleaned the TB and MAF sensor, changed plugs, checked for breaks dragging, running 38 lbs in tires, and checked the alinement, still getting 2 MPG less than last year.