My daughters low mileage RAV4 transmission fluid recently turned black. I check the fluid once a month, went from pink and sweet normal odor to black and no odor. No over heating, no codes, no driveability problems. We took it to a local shop and he is puzzled. The computer is not showing any overheating and the fluid does not smell burned. The shop drained and refilled the fluid, asked us to come back in 200 miles and he will drain again.(no charge for the second drain/refill)
Anybody have any ideas on what might be happening?
The transmission fluid is oxidized.
That’s why it’s black.
https://engineneeds.com/why-does-transmission-oil-turn-black/
Tester
It’s been my experience that Toyota factory trans fluid tends to turn dark quite early, without any burned smell or texture. Personally I think it’s just a characteristic of the factory fill fluid. I don’t see Toyota transmissions fail any sooner than any others. On the contrary, I think they’re pretty durable.
Changing it can’t hurt, but I wouldn’t lose any sleep over it.
In my environment, World Standard fluid is black after 100,000 miles of hot city driving, discolored after 50,000 miles.
Automatic transmission fluid was significantly improved 25 years ago, modern fluids may not have the same appearance as traditional fluids.
While not specifically about World Standard fluid, here is a note from an old Chrysler service bulletin regarding long life fluid:
FLUID COLOR
Mopar ATF+4(R) has exceptional durability. However, the red dye used in ATF+4(R) is not permanent; as the fluid ages it may become darker or appear brown in color. ATF+4(R) also has a unique odor that may change with age. With ATF+4(R) fluid, color and odor are no longer indicators of fluid condition and do not necessarily support a fluid change.