On Thu, 20 Jul 2017 19:50:59 -0700 (PDT),
trader_4 wrote:

Neither is the speedometer (to a few percent).

Few percent isn't good enough?

The whole point is that the calculations are off by more than people think,
so, the actual percentage matters greatly in that all the errors add up.

Speedo error adds to the fuel level error which adds to the fuel pump error
which adds to the density error which adds to the atmospheric pressure
error, etc.

All those errors add up, which is what my scientific mind sees.

I don't see mom-and-pop MPG-calculation accuracy anywhere near a decimal
point, that's for sure.

But that's why I asked the question (which is still unanswered since
references are all that matter - not opinions).