Castrol is offering FREE $10 Prepaid American Express Card with the purchase of 5-Quarts of Castrol Full Synthetic Motor Oil OR a Castrol Full Synthetic Oil Change from participating retailers for a limited time. Eligible products for purchase or Oil change includes Castrol GTX Full Synthetic, Castrol GTX Full Synthetic High Mileage, Castrol EDGE, Castrol EDGE High Mileage, Castrol EDGE Extended Performance, and Castrol EDGE Euro. Amazon and Walmart both have eligible products starting at $23.97 for a limited time. Limit one (1) Offers per household. Offer ends September 30, 2025.