TurboTed

I know Cummins recommends non-synthetic engine oil for the first 2 drains. I don't understand how this helps to seat the rings. I'd appreciate more information, or a further explanation.

HighTen

In some vehicles, synthetic motor oil changes things a lot. Sometimes it can raise fuel milage and decrease operating temperature. This is because synthetic motor oil is so much more lubricating and has a higher smoke point. In a new Cummins, you want the engine to get hot and you want the pistons and cylinder walls to grind on each other. Apparently, using synthetic will really increase the break in time. And when the rings aren't seated, they allow pressure to leak by.

I sure don't want to have a "slobbering" diesel longer than I have to.

y-knot

Give the engine time to seat itself before switching to your synthetic motor oil. I too use synthetic oil (Amsoil) and have for the last 9 vehicles. The worst mistake I ever made was to use it to soon. I switched at 900 miles once, and it took the engine a good 30,000 miles to seat. It would have a slight wisp of blue smoke on start-up. Finally once I made a good long heavy tow, it got broke-in, the power increased, mileage went up and the blue smoke went away.
Now I have a set routine, and stay with a quality non-synthetic motor oil till ready. At the 800 mile mark I change oil and filter, This change is to remove alot of the debris associated with in ital start-up and wear. Next oil and filter change occurs at the 2000 mile mark. Now the engine is starting to get it's seat and mileage and power are improving. If I can, I like to get a tow in around the end of this stage, nothing big, just a 50-100 mile run. Now at 4500 miles I will drain all fluids and replace with synthetics. That includes engine, transmission (new filter it automatic), front differential, rear differential, transfer case. Also if I have accessories to install, like MagHytec covers, trany pans, now is the time. If there is any EGT probes to install, they all go in before the last oil change. Same with any temp or pressure sensors. This way anything that made it's way into the oil system (Teflon tape, any dirt, etc) will be removed before the new lubricants are installed.
Also, I like to change air filters (or add the new intake system) at the 4500 mile mark. Take the time to look the truck over and make sure it clean(no oil or fluids). Also I grease any fittings that are present, and use synthetic grease. This has worked for me, and I will continue to brake vehicles in, in this manner.

TurboTed

Thanks y-knot! I pulled my trailer at 2000mi. for about 600miles (nothing to hard). I changed to synthetic at about 3500mi., for cold weather starts(5-40). I'll change back at about 8000mi.(15-40).

Vaughn MacKenzie

TurboTed since you towed 600 miles I think you're probably OK to stay with synthetics now that you've switched over. I would go ahead and give it another hard tow to two to help it along in the process though.

Vaughn

ppsi

This breakin issue is very interesting and was finally explained to me in a manner I could understand. If you baby an engine it will take forever to break in. The process involves cylinder pressure and what it does to the top compression ring. Just having the piston go up & down does not mate the cylinder/piston. What mated these two surfaces is high cylinder pressure caused by feeding the vehicle a lot of fuel AT THE PROPER RPM! How this works is when a vehicle is cruising at say 50 mph things are under a reasonable amt of momentum where if you mash the throttle the engine will respond by turning on the power w/o "bogging" like it might if flooring it from a stop or low speed. Now the secret (for some maybe) is when you mmash the throttle at a cruising speed the fuel gets dumped into the intake and causes a much higher cylinder pressure due tot he higher combustion. The real key is that this high pressure is forced onto the top of the piston, past the top of the piston/combustion ring (in an unbroken in motor) and behind the compression ring. The high pressure behind this top ring gets trapped for a short time between the inside of the ring groove and the ring causing the ring to press outwardly against the cylinder wall and speeding the mating process by higher friction due to the high cylinder pressure. I learned this the hard way when my 70 Challenger kept getting blowby through the valve cover breather whenever I "dragged it" from a stop. I took it out, as per this engine GURU's and cycled from 50 mph to about 90 mph by flooring it and letting off untill the speed bled down again. I did this about 10-15 times and no more blowby and the engine was all set. I did this same thing-w-my Ram after about 1000 fairly easy miles and I am still doing so once in a while after about 4k miles. Sorry for the long wind and any conflicting opinions are welcome.