So this comes up CONSTANTLY, but I haven’t seen an actual answer yet.
How is MPG calculated on both MAF and Speed Density vehicles?

Something I’ve always noticed, across all of my vehicles (all LS swapped trucks/SUVs/cars) is that the MPG is often wildly inaccurate. Now the math may very well be correct and the issue is that a sensor is reporting incorrectly, but KNOWING which sensors are being used, and what math is being applied, would be of massive assistance in troubleshooting issues.

EG: if the MAF is underreporting air mass, the MPG calculation I assume, would trend artificially high (as I’m guessing the MPG calc starts with MAF).

My newest build, I was seeing 26mpg (LS 6.0L in a 4500lbs truggy on 42″ shoes), and there’s just no way that’s accurate, but I already knew there was an issue with sensor data, as my trims were +70% combined on both banks on high load. I swapped MAF’s a few times and the one I’m running now shows single digit (erring on positive) trims, so it’s likely this MAF is more correct, but now I’m showing 13mpg which is massively artificially low. At the pump I’m measuring about 17-19mpg.

Any specifics on MPG calculations available anywhere?