in addition to the first post, the problems listed are more than likely different and seperate problems. the gas mileage being bad probably doesnt mean its because of the other problems.

my spark plugs were changed and I had a tune-up less than a year ago. my water pump has been replaced atleast twice. my 02 sensors were never changed, my oil filter was changed when i replaced the alternator, and i am having the coolant issue that is posted here...
http://www.contour.org/FAQ/FAQ.php?s=probs&displayid=21

i got another question, how much coolant is supposed to leave the container when the car is running? sometimes nothing is out, and sometimes about 2 centimeters below the max line is gone.

somtimes when it is very quiet, i notice a loud water rushing noise, like when you turn on a sink, but keep it barely flowing. like a hissing in the pipes. what could that be, a clog?

sorry for another long post, these are my first posts here.