Quote:
Originally Posted by KillerBeeZ
For those who are interested ... Mythbusters tested the windows down vs AC thing and found that running the AC with windows up is much better than no AC and windows down. While I don't agree with Mythbusters on many of their techniques (sometimes they don't use scientific method) I do agree on this one as their science was sound.
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They found this using an Expedition I believe, probably with a V8. For an engine of this size, yes, it is probably more efficient to use the A/C... the engine barely notices it at speed.
In a small, 4-cyl, A/C use puts a larger ratio of load onto the engine, so this curve of more efficient for windows vs. A/C likely changes. A/C takes a HUGE chunk of FE away at ANY speed, and is very noticeable on the highway, whereas windows down doesn't have as big an effect.
I also don't use MAX A/C because it causes the compressor to run constantly. If I have it to the "upper vent" position, you know, the picture of the seat with the arrow, and turn on the A/C, the compressor cycles itself at some point. I still self cycle at a higher temp though. Temperature dial is always at cold, because the compressor still runs, but heat is added from the coolant, as mentioned before, and is a waste.