Edwin Pawlowski wrote:

"Rich256" wrote in message
Or you can say you are paying about $5.50 an hour to drive 70 instead of
60
( or earning $5.50, tax free, driving at 60).

That is for the saved 29 hours. For the full time it is more like 91¢ per
hour.


The "Myth Busters" did a segment on driving with AC or windows open. It
was
not very conclusive I thought. I think the windows open won but the guy
with the AC on was freezing. They were not diving at 70 mph either.

I think speed and car design would make a difference. On a smaller engine,
the AC would take more power as a percentage than a larger engine. Years
ago, I'd shut the AC off to pass another car or to struggle up a hill. On my
car, I cannot feel any difference. Compressors have improved.

There's also a good probablility the computer cuts the compressor off
when you downshift automagically, too...

your "test"--I wouldn't put too much faith in the absolute values of
those onboard systems for small differences and short distances
particularly. Your data doesn't negate physical reality other than the
zero difference at the lower speed differential which is quite likely
owing to the imprecision of the display as much as anything (as you
note)....