On Wed, 19 Jul 2017 19:36:21 -0400,
wrote:

But of course, that fuel economy was based on odometer readings, which
are reading 26% low with the 19" tires. And the acceleration was only
slightly different because only the 1st gear part of the acceleration is
going to be changed much. After that, the gears keep the engine near
it's optimal power range for acceleration. On the highway, the engine
will be operating at 26% lower RPM, so depending on the power curve of
the engine, mileage could go either way.
I REALLY doubt it was "uncorrected" data, and the shiftpoints need
to be reprogrammed (if it is an automatic) or shift points changed by
the driver to optimize either mileage or accelleration. It is NOT a
simple calculation to determine which way mileage will go, or how to
drive the modified vehicle for best results.

I don't know how Car & Driver compensated for the things you guys talk
about, but what I find interesting is that they were not in the least
surprised that they had a relatively huge decrease in MPG when they ran
their tests.

Seems like they were not expecting an increase in MPG, that's for sure.