Found this on TunerPro forum from TGO forum. This is the equation used in 93V8S10 $OD, $OE, etc files
found an old post at TGO with instructions and a formula for calculating
instant MPG:

For the MPG conversation equation, use:


X/(C*0.0000212*Y*Z)

Where:

X = Vehicle Speed
Y =
Engine Speed
Z = Base Pulse Width
C = Injector constant (lbs/hr)
Have no idea what 0.0000212 is?

Then Robert said a better formula is
i use a different equation, one that works a bit more accurately for me...


A*(1/3600000)*(16.7)*(3)*E*(60)*(2) < What is 60? No mention below? I'm guessing 1/3600000 is 1 rpm?
where 16.7 is your injector
flowrate in lb/hr, the 3 represents half of the cylinders in the engine, and the
2 represents how many injector pulses per 4 stroke cycle(double fire, SFI or
single fire mode would need a 1). A is BPW in mSec, and E is RPM.

and
that will create a value showing injector flowrate in lb/hr.

A/6.073 < Is 6.073 the equation from above??

A is the value that was just created, and will
now create a injector flowrate in gallons/hour value.

A/B

A is MPH, B is gal/hr of fuel flow, then you'll have a MPG value.
Trying to figure out the more complex version from Robert, my questions are in Red above. This is for a MPG history table. For my LT1 it would be A*(1/3600000)*(24.87)*(4)*E*(60)*(1) if 60 is correct? And since it's SFI 1 is correct. With BPW of right and left divided by 2(R+L)/2

First one is easy...