Updates "Smooth Ride" 7/22/09. 1,000 city miles after new oil cooler, HHR overheated, towed back to Rydell in Van Nuys. No compression. Diagnosis: head gasket, cost $3000, estimated 4 days in shop. Week later, still in shop, they said the engine block was cracked, needs new engine, cost $6,000, ready five days later. So $1,100 for the oil cooler and service and $6,000 for the engine. Wish I had bought a 100,000 mile warranty. HHR is well maintained, mostly L.A. city driving. Only possible explanation for block cracking is quarterly 800 mile round trip at 75-80 mph. Too much for 4 cyl engine? Would not buy another American car without long warranty.
Engine block cracking at 71,000 miles is outrageous for any 2006 car. I would (1) stay away from any vehicle with this engine and (2) buy the long-term warranty on any American car.