[TRobinson6]

I dropped my tag lites to install brighter LEDs and noticed around the edge of the lens this black stuff that was crumbling. Was that supposed to be a gasket or was the black stuff just years of accumulated dirt

 

[jetfuel]

...dirt mixed with exhaust carbon...
...clean with a brush...reinstall with a thin layer of clear RTV (silicone)

Jetfuel...no more dirt

 

[duckhunter9090]

ther is a black rubber gasket. I clean mine when I change panel color every six months.