Pretty sure that is not oil spray but just capillary action causing the oil to move upward.
The gear cover plug is Cummins PN 3892666
One of my plugs is leaking about the same as yours and it was replaced about 40K miles ago. Probably have a finite life expectancy. If you find them get two.
For shiggles, I put in an RFQ on Alibaba to see what the per/unit price would be if we did a bulk buy. Seems to be $5-$10/ea. I'll update this thread when I know what Cummins charges and what...
ForeForums is user-supported. When you purchase through some links on our site, we may earn an affiliate commission.