Well here is what I have, just bought a 2004 3500 Diesel dually quad cab. The truck of my dreams. Have put about 1200 miles on it. It now has over 200,000 on it. It has smoke coming out of the bottom of the engine. It misses sometimes at idel but not all the time. I have used a quart of oil in 1,000 miles. It smells like oil burning in the engine compartment, but I can't see where it might be leaking. Any ideas as to where to start looking for the problem? I am running biodiesel in it at 50/50. It has a straight pipe from engine to the back, no muffler or cat. Thanks for all your help.

 

Check the valve covers towards the back of the motor

 

Already did it is not leaking from there. Anyother ideas? Thanks, Vicki