I have an engine with a rattle. I have pulled the exhaust no help, new plugs, air filter, oil&filter change. I am a mechanic so my foreman and i checked it out. We ruled out rods, crank, valvtrain. i checked for oil in water/water in oil. head gasket ok. plugs all looked good. engine starts and runs fine...lot's of power. we came to the possible conclusion that it's piston slap. the engine does have 196,000 miles on it so it would make sense. is this a common condition? how long will the engine last? should i go easy on it?...I do also own a trans am that is very fast but my Volvo is mu commuter wich i spend an hour in each day, and like to play with sometimes. also i am running high quality 15w40 oil in it due to it's milage. any ideas? thanks for your time ....Dan.