On Tue, 09 May 2006 13:13:31 -0400, Herbert Graf wrote:

>...
> Don't get me wrong, I can feel when the compressor turns on and off, I
> just find it odd that even with a bigger engine the extra energy used by
> the compressor doesn't appear to change the fuel mileage by any
> noticeable amount.

The first time I visited the 'States, in about 1992, I hired a car that had an onboard computer, cruise 
control, and Aircon.  I decided to play with all three, and set it up on a flat piece of road at a constant 
speed, then waited for the MPG reading to stabilise (about 33 if I remember rightly).  Then I turned on the 
Aircon, and it showed a drop of 5MPG.  I repeated the experiment a few times, and it was pretty consistent.

If you think about it, you are running an extra load from the engine - it *must* use some fuel to do it!  I 
don't know why your car doesn't seem to show this in practice.

Cheers,


Howard Winter
St.Albans, England


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