Automatic transmission fluid (ATF) is a highly specialized oil optimized for the special requirements of semi-automatic and automatic transmissions. There is a wide range of different Automatic Transmission Fluid and ATF formulations for different automatic gearboxes. OpieOils has a huge range that covers the requirements of nearly all vehicles.
Automatic transmissions can be very sensitive to the fluid used, so make sure you use one that's approved for your gearbox. You must also be careful to avoid any contamination. Some automatic transmissions do not use an ATF but a lightweight gear oil instead. Please check before purchase.