Too much blow by can only ruin a seal if the system relieving the crank case pressure isn't doing it's job. (plugged?) It takes more then an ounce or two of pressure in the crank case to blow a seal. I have a third gen, so I'm not intimatly familar with your crankcase vent system, but you might want to dismantle it all right back to the port in the valve cover and see if there is a plugged strainer/filter/valve or line between the port and the outlet of the vent system. Check the blow by at that port with the unit in idle, it will tell you how much you really have. As per the synthetic, more and more performance cars are coming out of the factory with synthetic oil in the crank case. It isn't the ideal breakin fluid for the Cummins but, with enough load anything will break in. If you crankcase vent system is in good shape, as all of the others have said, PUT A LOAD ON IT. It has to be worked to break it in. These engine started out in tractors and backhoes. Beat on it some. It isn't your wife, it will behave better if you beat on it once in a while. (not like it can call the cops on ya) [this is in no way shape or form an endorsment of spousal abuse] I've never been able to give my cummins a black eye. The wife has given me a few, but that's my own fault, I forgot the SAFE word.

 

I hope the heavy load pulling stops the blow by somewhat! So how many times and how far does a guy have to pull a heavy load? How much is heavy???

 

As heavy a load as you can put on there (up to the saftey ratings of course) and go and find the biggest hill you can find and just start pulling.

 

 

No, really. Big hill, steep and long. Do it once the engine is at full temp. Put your foot to the floor and don't back out until the electric fan clutch engages. And then do it again. I've heard stories of people buyin this units for getting groceries and the rings never seat and they end up with so much blow by their engine oil level actually goes up between changes. Again, it's a tractor engine. We'd tell ya to pull a plow but you'd have to buy different tires to get traction in the dirt. Plan B, Heavy trailer, big hill, and a cinder block for the throttle peddel. Borrow a trailer if ya have to, haul a load of wet sand, whatever it takes. (Note: Once you are over 50 mph [80kph] let of of the throttle to let the Torque converter to lock up so you don't fry your tranny.)