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.phpyou'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.