O’Reilly High Mileage ATF is an automatic transmission fluid that has been created for transmissions with more than 75,000 miles. It may be used in GM automatic transmission units that require the use of Dexron® IIIH or older fluids and is a qualified Ford Mercon® ATF. Further, it meets the performance requirements for Allison Transmission Division (C-4), and major hydraulic pump manufacturers’ requirements for antiwear hydraulic fluids. High Mileage ATF provides extra seal conditioning to help prevent leaks.