Ive got an 06 5.9 cummins auto, owned it for a little over a year now.   First 5k miles, it used a little bit of oil, maybe top of safe to middle section, so lets say 1.5 quarts?.  I have a leaking front crank seal(only visible oil leak), so I assumed it to be that.  I didnt care, wasnt using enough for me to worry at this point.

Previous owner had no issues, and was using Lucas long drain 15w-40 synthetic.  I changed the oil back in april to Rotella T6(5w-40) since the lucas stuff wasnt available in the area I lived.  Truck started mysteriously consuming more oil, no leaks visible anywhere on engine.  I havent done a proper compression check on it, but the ones you can do in your garage(oil cap test, and checking crank case breather), and both of those check out, no smoke, no air bubbles, and this is with a hot engine idling at 1500rpm.

I have fulled the charge air cooler boot in front of the turbo and it's bone dry.  Engine has amazing power, and starts in -30C degree wheather with no block heater without a problem.

Towards the end of the summer, I started loosing a lot of oil. maybe 2+ quarts every 500 miles.  The only thing I've noticed with the increase in oil consumption is that when I hit the accelerator with the window open it stunk like rotella t6 from the engine compartment(not the exhaust), a really strong smell of it.

 

With that said I can only assume I would see blue smoke with that much oil consumption if it were rings?  I have a turbo back exhaust so there no cat to catch any form of smoke. 

 

I spoke to the cummins tech at the dealer and he mentioned trying using 15w-40 Valvoline Premium Blue, which is the original oil for this engine, and run it for awhile watching the oil level before coming in for any expensive tests.

I have so far put on 150 or so miles and havent seen the oil level go down noticibly, my only concern with doing this is that I'm now running a 15W oil when temps can get below -30 here.. so I'm expecting to see harder starting this winter..Thinking of getting an oil pan heater, but I would much rather fix whatever is causing the oil consumption and go back to the 5W oil...

 

I've also checked the coolant for oil, and it's clean.

Transmission fluid is also clean

 

Any ideas as to what the problem is?  My only recourse at this point would be a compression and leakdown test in the event that the problem really is rings without smoke... or could I just be losing THAT MUCH oil from my front crank seal?  

 

Additionally the only problem I have had with the engine so far is that one day it threw a hole bunch of codes at me, FCA circuit open, fuel rail pressure too high, the limp mode code and #1 cylinder misfire. It turned out that the FCA wiring harness had come lose somehow, so I cleaned the contacts, and plugged it back in, did the same with the valve cover gasket wiring harness, I shot some electro contact cleaner in there and plugged them back in.  Those codes to this day have not come back, but during that time the engine ran like a bag of crap and belched out smoke like it was running on super overfuel, not sure if the smoke was blue or black, as it didn't last for more than a minute or two.

Edited December 23, 201311 yr by Joe989

I would guess your 02 is easier on the oil, my point was that the short life of CJ is the TBN primarily and fuel dilution is second. Neither of those should keep you from running 7500 miles but sample it if you are unsure.