why do i get better milage with ac on?

2004 CHEVROLET ASTRO
22,800 MILES
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ROBERTBRENDA
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04 astro AWD 4.3 vortec csfi auto trans 228,000 miles. I drive about 200 miles a day (windows always up). I normally use about 13 gallond fuel a day. The weather got warm I started running the ac. I now use about 10 gallons a day ac on. Any idea what is going on?
May 26, 2012 at 1:36 AM
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MHPAUTOS
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About the only thing that can affect this if the weather is very humid as well, the extra moisture and with the air being a little more denser can affect economy to a small degree but not to the extent you report, you may have noticed that on cool damp nights the car will run smoother and get a little better economy, same thing is going on.
May 26, 2012 at 1:41 AM
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ASEMASTER6371
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density of the air is critical map sensor and o2 sensors are very sensitive to atomspheric conditions.

roy
May 26, 2012 at 1:45 AM