Woke up this morning and noticed there's a puddle of dark fluid under the middle of my 2007 X5 3.0. It's CPO with about 55,000+ miles. I have not driven it for about the past 9 days (front brakes are due in only 180 more miles). Will have brakes done tomorrow (not by dealer but certified repair shop, $300 cheaper)...

Any ideas of what this leak is? The fluid is dark, not real oily, but slightly, no odor. The weather has recently changed from highs in the 80's last week, to the low's in the 50's this week (if that even matters). Could it be some type of sensor malfunction? Transmission fluid? Brake fluid?? I started it this morning to see if a service message would pop up, it didn't and when I checked, all systems were green, except the front brakes of course

I'm sure the repair shop can identify the source of the leak on tomorrow. I guess if it's something major, it would stilll be covered by the dealer under the CPO warranty up to $100,000 miles/6 years?

Thanks in advance!