From what I understand the transmission on the IS250 doesn't actually have a oil cooler. But instead we have a hockey puck looking heat exchanger on the side of the transmission with two hoses that circulate engine coolant from and back to the engine block. I understand this helps bring transmission oil up to temperature quicker. But what I would like to know is how is the transmission oil kept cool? If the exchanger brings it up to temperature, does it also help keep it cool?

 

Since it doesn't really have a heat exchange like older models. Where the lines lead up to the radiator. Its pretty much the addictives that help keep the tranny cool on a sealed unit.