Unfortunately, it's gallons of oil not of diesel.Started yesterday on a 600 mile round trip. Oil light was coming on as I got to my destination in Newburgh NY and I added 5qt. It had last been topped off ~1100 miles ago. I added a gallon when I got back to Rochester 300 miles later. I saw the oil light flash at me one more time after a bunch of idling and ~30mi of around town running after that, I'm REALLY hoping that was a fluke. It usually it has relatively high consumption, adding up to 1-3qt/1000 miles, but this is pretty unheard of.It's an external leak. The bottom of truck and trailer are well rustproofed again. Very very little on the bottom of the hood so it's not front main.I can see some oil on top of the timing housing near the water pump/idler pulley area, and after getting off the highway it looked like I had a decent amount puddled under the breather tube too - but the oil under the truck started further forward so it could just have been running down the outside of the tube too. KDP is tabbed, but it almost looks like a cracked timing housing. I crashed this truck about 1700 miles before I left on yesterday's 600 mile trip and it's been fine since, but it did touch the motor on the front passenger side (had to replace alt & bracket; fan, clutch, idler pulley; lower water neck was cracked when the fan hit it).It doesn't leak at all at idle that I could notice though. This is going to take some digging, I think. Booo.

Most common leaks that I have noticed are the tappet cover, timing case cover, and oil pan. The bolts on the bottom of the timing cover come loose a lot. I put some "never come out again (so my brother says)" stuff on those bolts and I think they are still tight but I'd have to check. I have my ppump off so I should probably finally take care of the tappet cover gasket.

It doesn't look to be the timing cover, unfortunately. I did a very good job reinstalling that when I did my cam, I'd had looseness and leaks quickly after putting this motor in. Everything got stripped down, cleaned up, gasket tack on both sides of new gaskets and all bolts were red locktited. I didn't sanity check myself and check any with a wrench yet though.I've got to get the belt off, pull the shroud and fan, pull that idler pulley and look behind it. Maybe I missed loctite on one and had a through-bolt fully back out and go away, giving me a massive leak right there? That'd be the best possible news...

Man, that SORKS! I hope it's something that can be easily fixed.

Not many gasket on these trucks. ISX is right most of the oil leaks are from the front cover or the tappet cover. Might just check out the vacuum pump seals too.

I found a broken vacuum line on my CAD crawling around underneath last night, so I'd have had at least a minor vacuum leak. Extra crank case pressure is never a good thing - but I know the breather isn't the only place it was exiting. I'm towing 12k 20-25 miles tomorrow morning and then returning at night with a near empty trailer, hopefully it does better than a quart lost