Castrol® GTX® High Mileage 20W-50 is specially formulated for vehicles with over 75,000 miles. It contains Phosphorus Replacement Technology, which reduces the level of phosphorus and replaces it with a proprietary additive that preserves your emission system while maintaining robust wear protection. Castrol® GTX® 20W-50 is formulated to clean away existing sludge while preventing new sludge formation to help extend engine life. It is also liquid engineered to resist viscosity and thermal breakdown.