Toyota releases the Genuine Automatic Transmission Fluid: ATF WS (World Standard) Specification (JWS3324 or NWS9638) in 2002. This fluid is not backward compatible with previous Toyota fluids or Dexron fluids. Almost all 2004 and above Toyota vehicles with automatic transmissions use the WS fluid specification. This fluid absorbs moisture and should never be reused. Always use fluid from an unopened container.
Under normal usage, the fluid has a 160,000 km (100,000 miles) maintenance interval for inspection only; ATF-WS does not require any flushing or changing during the life of the vehicle; however, an inspection of the maintenance schedule of many Toyota vehicles reveals that there is a 100,000 km (60,000 miles) replacement interval if the vehicle is used on short trips, city driving, hauling heavy loads, trailer towing, or using a car-top hauler.