"....blackish spot. Not red. Not solid black...." can be almost any fluid that
is up front
Coolant going bad
Steering fluid going bad
Engine oil with lots of oxidation/metal oxides/etc
Even brake fluid gone bad that has found a route to that point
If you are not willing to go 'up' there and find where it is coming from...then
you will continue to be at the mercy of whatever the mechanics say it is...
As others have recommended in the past...clean everything up there so that you
can see where it is coming from. Or if getting dirty is not your thing, then have
the dealer or better yet, an independent mechanic clean it and check it again later