I have various brands and weights of synthetic oils on hand. All purchased on major markdown, huge instant rebates or at closeout prices. My question is that which of the following will have the best "cleaning effect", if any. The vehicle is a 2000 Silverado 5.3 w/ 61,xxx miles. Oil filter will be Fram Ultra XG3675. OCI probably will be for 7500 miles. No mechanical problems with the vehicle. Pennz Ultra 5w-30 Pennz Plat 10w-30 Castrol Edge Ti Extended Performance 5w-30 or 10w-30. Valvoline MaxLife Syn-Blend 5w-30 or 10w-30 (with or without a quart of MMO) Thanks for your input and suggestions.