I think it's water from the A/C. Mine has begun doing the same thing, dripping water just rear of the front wheels, two spots side-by-side in the tranny area. It will drip for 2+ days in the garage and when I back her out, it will leave a trail on the floor as I back out. I recently had some work done at my Indy and I think they removed the lower pan access panels and didn't replace them. I always wondered where all of that A/C condensation water was going - it was being held in the underpan and must be dispersed as you drive?

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2022 X6///M - Toronto Red, Silverstone Full Merino Leather, Executive Package w/Remote Engine Start, Soft-close doors, Heated & Cooled Cupholders, Front Ventilated Seats, Front & Rear Heated Seats, Front Massaging Seats, Carbon Fiber Trim.

2002 X5 3.0i, Sport Premium, Titanium Silver, Grey Dakota, Cold Weather Pkg, Xenons, DICE, LED Tails, just a winter vehicle...

2007 550i, Sport Premium, Silver Grey Metallic, Grey Dakota, Nav, Cold Weather Pkg, Comfort Access, HD Radio, Xenons.