Mechanics

WHY DO I GET BETTER MILAGE WITH AC ON?

2004 Chevrolet Astro • 22,800 miles

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?
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ROBERTBRENDA
May 26, 2012.



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.

Mhpautos
May 26, 2012.
Density of the air is critical map sensor and o2 sensors are very sensitive to atomspheric conditions.

Roy

ASEMaster6371
May 26, 2012.