Bought my 2005 4 door base model cobalt new 09/05. I bought a "cheap" model, so, my expectations were commensurate. 79,520 miles later I am quite pleased with my investment. Only problems to date, ignition coil went out at 23,000 miles, warranty replacement. Also, A/C evap drain was plugged with insulation on the firewall, allowing condensate water to drain inside the vehicle passenger side front. this I found myself, after dealer said no problems detected. Tire pressures checked min. of twice/week. rotate every 5,000 miles along with the oil changes, only have used synthetic 5/30. new air filter every 10k, replace HVAC filter spring/fall, plugs every 25,000 miles. fun to drive and own!
ecotec 2.2l engine, the battery in the trunk makes for ample room under hood for DIY repairs, oil filter design is less messy to change than most other vehicles, cockpit is comfortable.