I use Pennzoil Platinum Full Synthetic 5-30 and find it runs cooler and quiets the valve train.
You can purchase it @ Wal-Mart for $20 and with a $15 mail in coupon, it’s only $1 a quart.
I change my oil every 3K to 4K depending on my driving. You can stockpile by giving different names & addresses for the rebate (use cash).
http://www.pennzoil.com/documents/04...ine%20form.pdf