"Harry K" wrote in message
ups.com...

It is a useable instrument to detect what mode of driving is most
efficient even it it is not accurate. That is if it reports, for
example, 19 mpg over a stretch of road with tailgate down and then you
repeat the run in the same direction, same speed, same conditions,
etc. the reported mpg is then a useable bit of data. Yes, it will be
inaccurate but the comparison is useable and meaningful.

I would not assume that a faulty instrument is going to give me readings
that are inaccurate in a consistent way across a given range.

-Scott