For vehicles over 100,000 miles, the recommended synthetic oil you should use a full synthetic, as opposed to a semi-synthetic oil. The brand and viscosity of oil doesn’t matter as much as the type of synthetic you are putting into your vehicle. Full synthetics will lube the engine better and are designed for longer life and reduced vehicles emissions. In addition, a full synthetic will provide better fuel economy and overall performance. However, it should be noted that synthetic oils are typically thinner. Should your vehicle possess a leak, it is likely a synthetic oil will leak slightly more than a traditional oil.