Nunzzio, here is a great thread:
http://www.986forum.com/forums/showthread.php?t=7567&highlight=winter+storage
This is a key part from MNBoxster:
"You can do this in one of two ways. First, if a Manual, put the car in Neutral and push it back a few feet. Then, place the gearshift in 5th gear and push the car forward, this will rotate the engine. If you run out of room, say in a garage, go to neutral again and repeat procedure so you're sure one complete revolution of the engine has occured. This will loosen any frozen engine parts (such as rings, chains, etc.), without the extreme torque of the starter motor. This torque is so great that it can tear rings or do other damage. If you have a TipS car, take a large socket on a breaker bar and turn the crankshaft pulley bolt clockwise to rotate the engine. "
Threaded Mode
