The use of the BMW valve cover gaskets and seals is to stop the most common place for oil to leak out of your engine. These are very different than the type of material used for many years previously. Today the valve cover gaskets and seals used on all BMW's are made out of a special polymer. The performance improvement of this new material includes its resistance to oil and heat to a greater degree than the cork gaskets and the polymers first used in gaskets just a few years ago. While the material used for stopping oil leaks has changed the manner in which the valve cover gaskets and seals are put in place has not. Both surfaces of your BMW engine where the seals and gaskets will be placed must be clean and free of oil and dirt. This will make it possible for the barrier to prevent oil from penetrating it. Another procedure that has not changed is just how the valve cover gaskets and seals are tightened down. The first valve cover bolts that are tightened down are the ones in the middle. The process alternates sides and ends until the last one is put into place. Most technicians also do the tightening portion of this process in steps. The first is to just get the bolts snug, then tightening them to the specified torque. Over tightening the bolts will squeeze the gasket to the point it could cause a crack and oil will leak from that point. The BMW valve cover gasket and seals are made for the specific engine and model year of your automobile. There are some similarities between them but they are not interchangeable. By always using the correct valve cover gasket and seals for your BMW, not only will the oil remain in the engine where it is useful, but the outside of the engine will stay clean.