I have a 8.3 in a 2000 Freightliner Fl 60 and it want to leak oil out at 70 mph and a lot less at 55. I thought it was the main seal so replaced it , now it's clean up front but still wet from the back. I went 30 miles into the wind at 70 and used about 3gals. Then turned around and did 55 and used about one gal.
UV dye
Maybe your crankcase breather is plugged. The engine will build pressure and force oil out.
Pressure wash the engine off and run it at a higher rpm's for a while, its not the speed your traveling at but the rpm's the engine runs at, watch it to see where it leaks from then, also check blowby at idle or remove the breather cap completely to see if that helps. As much as its puking out, it shouldn't be hard to see where its leaking from.
It looks like the air compresser,at 2000 RPM it was blowing out a great deal of air from the suction side. When connected to the intake it blew out the vent tube that has the turbo drain tube running past it. I think it had the effect of a siphon valve. We found a new one for a 1000$ but I still don't feel lucky. Maybe if it works I will feel better.
If that solves the problem, it was a cheap fix compared to some other things that could have been wrong.
I made the same trip as Sunday night but did 70 over and 75 back and could not see any drop of oil level
It sounds like your compressor was dumping oil by the compressor pistons, when compressor was unloaded (basically holding intake reed plates open, this oil went right into the intake and burned through the combustion chambers. If that's the case, it's very likely your faulty compressor has now fouled the air dryer when it's compressing. I think you should take a good look at it.
I'll add to what willie said, pull the receiver dryer off and if there's oil in it, flush the lines to it, and also check the lines after it for oil residue, if it doesn't have a receiver dryer [some don't] check now before your entire system is blown full of engine oil and you have to fight that ordeal too, keep cleaning till you find where the oil ended. Best of luck
There are still some mysteries to be solved, I have no dryer and my air tanks are clean.the oil was all down the right side and bottom of the truck.the engin has 160,000 on I Cummins inframe and 660,000 on the truck.after the inframe I started replacing all the other stuff but spaced out. So the compresser was the last piece with the most miles on it.
PS the truck is now fixed ,about 3 months ago. Never found problem and put in a used engine with more power.
If you remove the air compressor inspect the front cover very close they have a huge tendency to crack. They are made of aluminum and don't support the compressor and injection pump very good especially in off road conditions...TIO