If you're driving an American classic with or without catalytic converters, we have what your engine needs. These oils contain the "correct" amount of Zinc for proper protection but also catalytic converter safe. Whether that be GTX 10w40 (for vehicles 1978 to 1993) or one of the 'Classic' series oils depending on your car's age and requirements. Check your owners manual or email us at: sales@classicoilsUSA.com We'll be happy to help!