Thanks all!
It is diesel fuel.
Pic 1 is sideways, Pic 2 is upside down, Pic 3 is sideways, Pic 4 is fine.
It is leaking from around the fuel/water separator filter at the top and bottom, as well as dripping onto the ground from what appears to be an overflow hose? It has a 4" rubber hose coming off the filter and emptying onto the ground beneath the coach (just like an old radiator overflow tube coming off a radiator cap) PIC 2. I tried to show it in the pics above, but it was pretty dark. It's a short little tube on the right (or left when upside down) in PIC 2 taken from under the bay. I don't know what that large oil tank is for in PIC 1 but it always seems to be oily and dirty around the cap and on the side, no matter how often I clean it. Is that tranny fluid, power steering fluid, etc?
I'm glad to hear it's not a huge crisis, but I need to figure out how to fix it soon. It's made a puddle under the coach as seen in PIC 3, and it's got that diesel smell.
Anyone have any idea what that Racor panel PIC 4 is for with the "air purge" and "H2O purge" buttons?
If so, how do I use it?