5.3 LY5 idle fuel consumption rate

[DJPepper]

I was trying to find out how much fuel my 2008 Sierra 5.3 LY5 burns at idle. I'm logging mpg from running stock, running only in 3rd gear ( to stop the afm from activating), oil catch can installed in line with pcv, updated valve cover thats supposed to reduce oil consumption through the pcv system, after new plugs and wires (and possibly top engine cleaner depending what the combustion chambers look like), and I'll eventually get a tune so I can use OD without cylinder deactivation coming on. I'm urban camping while I save for a boat to use as a condo on the water. Last week was way hotter and I let my truck idle for AC and to use my inverter much longer than usual.I was hoping to find my idle fuel consumption rate to correct my numbers. Is this possible with a tech 2 clone? I've been through all of the settings and data options and can't find anything. Or what's a good estimate to use?