 I have had nothing but great reliability with my 2002 Focus ZTS.  I still have the factory battery in it, ac works great, great on gas, I can always depend on this car to get me where I need to go.  Oil always gets changed on a regular basis, regular check ups and it has been going.  I'm no mechanic but the money that I have put into this car is just maintenance that you do for your car to keep running.  The only thing that has not worked since I purchased it was the drivers side windshield wiper.