I bought some GL5 gear oil for my rear diff, and I was wondering if I could use it in my transmission as well. It's a 535i with the getrag 260/5 and it has a red ATF sticker on it. Does that mean ATF is required or just a suggestion? I'd really like to use this oil since it gets too cold for whatever fluid is in there now (the car primarily lived in Texas, before coming with me to Worcester).

Thanks in advance.