Help: What is the ATF Oil cap for?
 

I noticed in the engine compartment on the driver side next to the oil dip stick, there is a cap labelled "ATF Oil", I first got confused with the engine oil cap, but that is located on the top left side of the engine with a "castrol" marking. I looked at the owners handbook but there is no mention of the ATF oil cap and the information regarding the engine oil cap is very vague and of poor quality. Thanks for enlightening me on this mystery!

ATF
Automatic Transmission Fluid

Agree that ATF stands for Automatic Transmission Fluid, but in this case I think that refers to the contents of the reservoir, and not the component.

Suspect the OP is referring to the power steering reservoir, which uses ATF.

JCL, it is pwr steering...
I have a 5 spd manual trans and also
have that cap and reservoir.
BR,md

I understand the X5 has a closed system for the Auto-transmission. You do not refill it.

Just for clarification, I was simply letting him know what the letters ATF stand for :)