10 is low. I was getting 13-15 with all terrain tires and metal bumpers on 87 gas

 

I know it's low. But I'm mystified as to why it has been the same story on both of my trucks.
And this is after hundreds of miles of driving after component replacement. Adaptive values should have adjusted. (I don't have a code device that will reset them.)

 

I see one common denominator between the two trucks: The driver. Cruising down the highway, if I keep her at or near 65, I have seen as high as 15mpg, a steady 50mph will net around 17. above 70, it drops to single digits. I generally average 13.

 

Yep, I'm aware that the driver can have a huge effect on the mpg. The highest mpg I've ever had has been while overlanding, when speeds were pretty slow and there were effectively no aerodynamics in play.
One of the problems in my area is that if you try to keep anywhere near 50-65mph, you'll be run down by some cigar-chompin' grandma in an Escalade on her way to the NJ outlet malls.

To bring it back to the OP, how long has it been since all of that work was done? Has the system had time to adjust and implement new adaptive settings?

 

Keep in mind that your ultragauge has no way to actually know your current MPG. It is making an estimate. No signal from the ECU for MPG.

 

I track it with Fuelly for accuracy, and only rely on the Ultragauge for on-the-fly estimates.

 

These codes popped up

Was open loop then closed.
They are new walker O2 upstream sensors.

 

That is the problem. These rigs are not designed for highspeed use. They can do it easily, but have the aerodynamics to rival a brick. The faster you go, the more fuel you are going to use. Like I mentioned, I get it above 70, I drop to single digits.

 

I can consistently get 15.5 mpg over 120 miles of freeway at 75 mph. I don't know why your truck would be different.

That is running 92 octane premium. Using cruise control doesn't seem to make much difference. I normally don't.

 

I keep it below 70, I get 13 to 15 depending on the wind (it's flat here) I get above 70 and drops like a rock.