Bad A/C compressor
On a long trip this weekend my 97 escort got horrible gas mileage ~(22mph) for the first few tanks, so after the second fill up I decided to look and see what was wrong and I noticed that the belt tensioner was bouncing and there was a squeaking noise. I thought that maybe the tensioner pully was going out so I pulled it off and replaced it (the old one did have a slight wobble and grinding sound to it); but that didn't fix it. But then I noticed that the bouncing only happened when the a/c kicked on, so we just turned the a/c off for the next tank and our gas mileage went back to normal (32mph).
Is the A/C compressor going out? I was told that when the compressor goes bad it just freezes.