Castrol® EDGE® High Mileage 10W-40 is an advanced full synthetic motor oil that is specifically designed for vehicles with over 75,000 miles. It's been engineered to reduce leaks, burnoff and power robbing deposits, but also contains a proprietary additive to protect the emission system. Our Phosphorus Replacement Technology reduces harmful phosphorus to protect the catalytic converter and extend maximum performance. It is the natural choice for drivers who demand maximum performance from their high mileage car.