Gray green substance under oil cap - Cummins ISX15

[Rawze]

(03-05-2021 )SupVit Wrote:  ... went to the Cummins dealer to test the fuel system, they did not find anything.
...Went to Rush Center - same result.
...
Went to experienced mechanic -same. Few thousand dollars wasted
...

sounds to me like you've been taking it to the wrong places.

Most OE cerrtified places are nothing but gaggle of clueless idiots who r trained to do thing but put a computer on it, sell you the most expensive solution to put out the fire while solving little to no problems, and take your money!