275k on the clock. Starts smoothly every time. No smoke on start up. No smoke while driving. Wonderful power and smooth acceleration. Cruises at 80 mph with ease. Loves oil! LOL

After I purchased the car a few months ago I noticed oil on the outside of the IP at the bottom of the ALDA. Oil was also present around the intake where the boost line connects. No oil at the tail pipe though. It has been my assumption that the oil is getting into the intake and being pushed out the boost line down to the ALDA. I put new seals and such in the turbo in hopes that that would fix the issue. I want to deny the bent rod issue as long as I can. LOL. New seals did not solve the oil in the intake issue. It is now obvious that the oil is coming from the valve cover breather hose because of blow by. I know, I could've checked this first but why do things the easy way when you can have so much fun going around the mountain? Anyway, I now have a small amount of oil exiting via the tail pipe. Today I removed the injectors to see if I was pumping oil out of any of the cylinders and each injector tip was dry and clean. The crossover is wet and when I disconnected the breather hose from the air intake tube at the turbo inlet and ran the car down the road I had plenty of oil spray out of the hose.

I am not devastated by the thought of a failing engine. I have a driveway full of drivers. I'm having a hard time giving in to a bent rod though. The oil consumption can vary from 1qt per 1200 miles to 1qt per 300 miles depending on how it's driven. I'll do a compression test next week to have more data but I am amazed at how well and stout this car runs.....if it IS a bent rod. Yes, I have denial issues.

I have the same car. Mine has 329,600 on the clock. It has been using about a quart of oil every 2000 miles - I think most of it going into the intake. For many years, I used Rotella 15w40 and changed every 5000. Earlier this year I switched to Mobil 1 10w40. (consumption seemed about the same but engine was quieter). Last oil change, I went to Mobil 1 15W50 (at 335k). It used one quart in the first 3500 miles, so it was an improvement.

I'm not sure if this is a coincidence or not, but I changed the timing chain over the Thanksgiving weekend. This week I made a round trip to Dallas which was 700 total miles of almost all Interstate. Cruise set at 75 mph most of the time with an occasional 80. I checked the oil before I started back and it was full. Again at home today and still full. I wouldn't think that timing would have anything to do with oil consumption. I don't take this car on many road trips so I don't really have any history to refer to as for how much oil it uses on long trips.

I appears to me that either the change of viscosity of the oil, and/or the timing change has resulted in reduced oil consumption. I will need more time to watch it. It's almost oil change time now.

My daughter drove this car for the first several years that I owned it. I've just started driving it as a "company car" for my work about 9 months ago. In that time, I've been spending what they reimburse me for mileage on getting the car in shape. It's getting there!

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1991 350SDL 350k+ miles

LOL! I was in the garage a little while ago tinkering with the car and decided I'd just put my thumb over the valve cover breather hose while the engine was running. Within 15 seconds the engine began to die out but never shut down. I walked around to the back of the car and there was an 18" diameter puddle of black oil underneath the tail pipe. Hahaha! I am amazed that this engine runs so smooth. Amazed!

Build a catch can to catch the oil. Then pour it back in! Might get a few more miles out of it that way.

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1991 350SDL 350k+ miles

It's a rare 602/3 head gasket that's tight after 275K miles. My unsubstantiated opinion is that oil getting past the head gasket into the cylinder combined with EGR soot contributes if not causes bent rods.

Remove the pipe that feeds exhaust gas to the turbo to check if it's as oily as the exhaust pipe tips. If its not, the turbo seals are failing allowing oil into the exhaust stream downstream of the engine. If it is, my money's on failing exhaust valve stem seals. Generally, oil that gets into the combustion chambers is burned and unlikely to get past the exhaust valve as liquid oil rather than a plume of smoke. Enough oil getting into the cylinders to remain liquid all the way down the exhaust system would likely hydrolock the engine.

Sixto
MB-less

I did a compression test on the engine of my '91 350SDL today and here are the results:
#1- 440
#2- 420
#3- 420
#4- 435
#5- 440
#6- 425

When I removed the injectors today every one of them was clean and dry on the tip so....? When cranking the engine there is no "oil mist" from any cylinder. I'll dig deeper if necessary. I'm at a standstill at this point. Any tips on what to do next would be appreciated.

Blowby wouldn't make oil come out the exhaust pipe - really only a turbo failure would do that.

If you unhook the breather tube and remove the oil filler cap how much blow by to you see?

I would think that if the engine had so much loss of sealing that it was blowing oil out the tail pipe it would hardly run. Plus being a diesel it would tend to run away.

With oil in the crossover I'd really suspect the turbo. That's how I noticed when my turbo was going out. Be careful - a slug of oil in the intake can bend rods on any motor, let alone one known to be sensitive!

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

There's no blow by noticeable by sight. If I hold my thumb over the breather tube then there's plenty of pressure build up that the engine will begin to die out within 15 seconds. There's oil in the crossover and intake of course. I put new seals in the turbo several weeks ago in hopes that it would reduce the oil consumption but now it's worse and dripping out the tail pipe. I must've goofed when I put the seals in. I guess I'll remove the turbo again and see what's going on there.

This engine starts and runs smoothly and has plenty of power though. I love the ride and drive.

Hm. Say you loosen but don't remove the oil filler cap. Does the blowby push the cap off the valve cover?

Do your power brakes work (the vacuum pump empties into the crankcase, so a large vacuum leak will create lots of "blow by")?

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Brakes work great and so do all the other vacuum related components. Sometimes the center vents don't work until you get moving but there are no signs of vacuum failure that I can tell.

Referring to my earlier post about the oil consumption being less after changing oil viscosity and the timing chain....I also replaced the vacuum pump with a used, upgraded model at the same time I replaced the timing chain. I wonder if the old vacuum pump was bad contributing to the oil consumption? Possible?

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1991 350SDL 350k+ miles