A different Air Con and FE question

[billk]

Originally Posted by *MAD DOG*

Ok, Who can answer this?

If i'm driving my car with the air con on and the fan on 4 does that use more fuel than if i have the air con on and the fan on 3, 2 or 1?

I say the a/c will run longer with the fan on 4, and this will use more fuel. This is because the faster the fan blows, the less temperature drop you will have across the a/c evaporator. so faster air will result in the air not being as cold, which means it will take longer to cool. I know this sounds stupid, but the slower the fan moves, the colder the air out the vent will be. So if the fan is on low, colder air will coming out the vent, which will result in the thermostat reaching temp faster, which will cause the compressor to turn off sooner.
I know on a hot day, fan on high cools the car faster, but lower the fan speed after a few minutes, and it will cool even faster.