I recommend that you avoid the synthetic blend entirely and select either the straight mineral-oil (standard grade) or full-synthetic. Ask yourself what you are after in the motor oil. If you are following the recommended drain intervals you gain nothing by using synthetics - you're pouring money, and good oil, down the drain at each change. The advantage to full-synthetic is in very cold flow characteristics (read: -20F - type environments) and extended drain intervals. Full-synthetic oils will last well past 15K miles without breaking down although you MUST change your oil filter at the recommended intervals since they will clog and then bypass. Synthetic blends are not regulated; how much synthetic is in the blend? 50%? 20%? 5%? The standard mineral-based oils will do just fine under the recommended drain intervals.