A/C only cools to 55 degrees from vents, while driving. It feels somewhat comfortable. I would think at max cooling it should blow out near 40 degree air. Also theres not much cooling / heat change on the temp control. Its max cold, then just slide selector to the right 1/4 inch and air becomes hot. Whats up?

 

55 degree on a what temperature day? and where do you live? humidity?
normally if you are only a 75-80 degree day, the A/C will only cool down to 50 degree on Recirculation mode. 55 seems normal to me.
No A/C will go down to 40 degree, you have to remember, water freeze at 32 degree, your Evaporator will become a block of Ice if you expect the vent temp to be 40.

 

Well it was 111. I live along the colorado river in AZ. Usually minimal humidity though today a monsoon came thru. Theres just no adjusting temp though, and compressor is on all the time . There goes my mpg.