We own a 2005 Malibu (V6 3.5L), purchased new almost 4 years ago. Now the car has 93,000 miles on it and we are wondering whether or not to replace the vehicle. What are common problems with high-mileage malibus? What kind of repair costs are we looking at in the future? The car has been well-maintained, synthetic oil, changed when suggested by our mechanic and other normal maintenance such as brakes and tires, no other major issues although our mechanic thinks we have a spark plug misfiring as we get a little studder when it starts occasionally and the coolant light sporadically comes on. ~thanks