1986/turbo/250,000mi/400,000klm....(no puddles of oil on the driveway) ...I have to add about a liter of oil at every full tank (about 800klm.)...and yet even though the winters have been mild, there have been some days that were -10C and the car starts immediately with one cycle of the glow plugs.. no compression test has been done yet...I am thinking that the compression is still good since it starts right up...is there a possibility that the "oil control rings" could be the main problem here
I had a 1.6TD, 435psi+ (iirc) ran great except slowly came back to idle after reving, and it used a qt/200mi. Honed and replaced the rings and all's well. Yes, the oil control rings can fail and you still have great running and compression. You might want to change the valve seals and try that first though.
On the otherhand, oil is cheap. Just keep runnin her.
1986/turbo/250,000mi/400,000klm....(no puddles of oil on the driveway) ...I have to add about a liter of oil at every full tank (about 800klm.)...and yet even though the winters have been mild, there have been some days that were -10C and the car starts immediately with one cycle of the glow plugs.. no compression test has been done yet...I am thinking that the compression is still good since it starts right up...is there a possibility that the "oil control rings" could be the main problem here
Not unusual to have an oil loss problem on a car with that many kms. Is there any oil smoke coming out of it? If there is smoke all the time it is probably rings. If the smoke is mostly when you start it then it is probably valve stem seals.
I think the earlier posting seems to agree with me that the excessive oil consumption has more to do with the "oil control" rings, then "compression" rings..the car starts immed.right up and you can drive/no problems..no excessive oil showing from the exhaust when driving around town...a compression test will somewhat tell the story.....it reminds me of many years ago that when I bought a new 85 golf diesel, that shortly after 100,000 klm. it started useing a lot(20/50) of oil and never stopped doing it until I replaced it at 500,000 klm....yet another example of an opposite situation, is when I simply replaced rings on a very tired motor and then got 2500klm\1 liter oil while the compression was very near the min. requirement...
Let me give another data point that the oil control rings can go bad, causing excessive oil consumption, while the compresson rings can still be working fine.
I had an oil consumption issue on the 1.6 VNTD Rabbit (the turbo had nothing to do with it by the way, as this problem had been developing and was present long before the turbo). The car always started right up in the cold and ran great, had no sign of weak compression, but was consuming a quart here and there which would have been quite expensive on the synthetic which IMO every turbo application should use. I did some tests to make sure it all wasn't going out the crankcase vent... there was in fact very little oil getting out that way, so it wasn't excessive blowby. There was also often a blueish oily smoke color out the exhaust. The smoking did not go away after fixing a loose timing belt I found during turbo installation, rebuilding fuel injectors, swapping to a different turbo-diesel fuel injection pump, and adding the turbo, so that pretty much ruled out the smoking being a possible diesel injection problem.
DieselsRcool helped me change out the valve stem seals... it did not cure the problem. Then mostly on his suggestion, I changed the rings and dingleberry-honed the cylinder walls. The re-ring completely solved the oil consumption issue... The exhaust is now totally clean, and the oil sump level stays almost rock solid now!
I should mention that the engine was rebuilt at one point long time before from the previous owner, so it didn't have the OEM rings.
Make sure you inspect the turbo before tearing into the engine. Check the intake piping from the turbo to the intake manifold for oil, and check the turbine side for oil.