Pretty sure she's burning it. A few months after I bought her, I suspected rear main seal but it turned out to be the oil cooler. Whew. Now there are only a few drops in a night, and not much under the truck. So it must be going out the tailpipes. 4.10 gears, a 4spd, and a guy who commuted 100 Texas freeway miles each way every work day...well you get the picture. She spent too much time at high rpm. Now with the 5spd it's much better. She uses a quart every tank and a half, one 38 gallon tank.

 

6.9's were notorious for using a little oil from day one. Every one I talk to that owned one new said they took a quart or so every couple of tanks of fuel. There was also a tsb for high oil consumption.

I've been chasing leaks on mine since the dawn of time. When I did my motor swap I resealed the used engine while it was out. Ended up with a front main leak, a front cover to oil pan leak, after I fixed those the intake manifold at the rear of the block started to leak. I spent several days doing nothing but cleaning and prepping surfaces for reseal and still ended up with leaks.

I blame internationals second ring gap which causes blow by from day one and slightly pressurises the crankcase.

Head gaskets have been changed and there leaking again in the corners. (Very common for a 6.9)

I just put oil in it and run it. I could buy a drum a month and it's still cheaper than a new truck payment and someone has to keep the asphalt oiled. Been considering billing the county..

 

I always assume that the extra oil leakage is rust prevention - it keeps the (front half) of the frame, oil pan etc from rusting!

And yeah, it's pretty rare to find an IDI without some sort of oil leak...

 

The only ones I've seen that don't leak are ones that have been sitting and once you put them back on the road fulltime they start leaking again.

Call it an "up north package"

Outside of the coastal areas we are very blessed with little to no rust in Texas. Farmer beds are bad about rusting through from buildup of hay/cotton seed and liquid fertilizer, but outside of that most stuff is just surface rust. Nothing ospho or por15 won't take care of. Just don't get it on your hands!

There's enough oil in the bottom of my bed from working it should outlast me..