On Thu, 20 Jul 2017 08:39:22 -0600,
rbowman wrote:

Here's a seemingly expensive "fuel economy meter" which shows the
complexity of calibration, heated probes, high-speed sampling, auto zero,
etc. whose specs show a "resolution" of "± 2% reading" and a "repatability"
of "±2 % of reading" with a "span drift" of "±2 % of reading"
http://mustangae.com/products-servic...+Economy+Meter
http://mustangdyne.com/mustangae/upd...09/MAE-FEM.pdf

OBCII. You are plugged into the car's computer system, air mass sensors,
injector timing, the whole works.

Since mpg measurement at home is a tangent offshoot from mpg performance of
larger-diameter wheels and tires, I opened a separate thread with the
science guys over here

https://groups.google.com/forum/#!to...ir/PT3YdPClM7g
What is the realistic accuracy & precision of typical consumer MPG
calculations (tripmeter miles/pump gallons)