Before switching its a good idea to do a cleaning on the motor.  Amsoil makes a flush for this.  A better but more expensive choice is AutoRX.

go to http://theoildrop.server101.com/ubb/ultimatebb.php
you'll learn everything you want to know about oil and more.

I'm new to this oil stuff, been doing it for about a year now.  The learning curve is steep once you find a good source for info.  I send my used oil out for analysis now to monitor how my vehicles and the oil are doing.  It's spendy but kinda facinating.