It is not possible for the unregulated engine oil to enter the injection delivery valves.

* Engine oil pressure is roughly 3 bar = roughly 45 PSI.
* Delivery valve pressure is over 1300 pounds.
* On a prefect system; Fuel lift pump pressure should be 25 to 30 psi, please note the roller/plunger mounts into the injection pump crankcase/oil sump which should be just above atmospheric pressure.

fuel pressure

Lift Pump Rebuild...


Note: I begin to suspect piston rings and valve guides may be the issue.

Now that's useful information! I was trying to understand the threads about oil getting into fuel from IP and conceptualize how it could be drawn into the lift pump, especially in the volume I'm experiencing. So, with clean fuel throughout the tank in my primary filter there likely isn't any oil making it's way from the IP through the lift pump into the fuel supply. Check that off. I've got the later single-line piston vacuum pump. Check that off. I've removed the breather tube and replaced with clamp-on filter and still used oil, so not breather ingestion. Check that off. There's absolutely no leakage or dripping from the engine or any other part of the car. Check that off. So that leaves the head gasket issue mentioned earlier which I'll test for this weekend when doing another compression test, and the possibility of bad oil rings, or a combination. Anything else we haven't visited or revisited?

__________________
Joe Black
Get yellow fever at ACME!

Just the MB's: '82 300DT (stick), '81 240D, '80 300SD, '80 300D, '81 240D Manual

Unfortunately, no.

Okay, last three hundred miles I've been topping the oil to the middle mark each 100 miles and each time it takes between 2 and 2 1/4 quarts. By this time all the Lucas Oil Stabilizer is likely out the tailpipe so apparently it had little affect on consumption as I originally thought, so a total waste of $30. I'm going to keep checking each 100 miles as that'll establish a good record I think. Something new I noticed at the last oil check is that the oil cooler is cool to the touch. The only part of it warm is at the top where the bracket touches the radiator, so it's just warm from thermal conduction. I checked while the engine was still running after driving about 35 highway miles, so it should have been pretty warm. The rubber portion of the oil cooler lines were warm, so maybe the cooler itself is blocked internally. Anyone ever encounter this? I doubt it has anything to do with oil consumption but just something else I need to address before selling.

__________________
Joe Black
Get yellow fever at ACME!

Just the MB's: '82 300DT (stick), '81 240D, '80 300SD, '80 300D, '81 240D Manual

Oil cooler obstructed not likely. Thermostat in the oil filter area may have died from old age and use. Either way the engine can survive well with no oil cooler working I would think. Or the oil is not reaching enough temperature to open that thermostat.

Just has hotter oil than preffered at worse. A lot of engine heat is removed by the oil. Though some 616 and perhaps some 617s have no oil cooler. I always considered it a boost to keep the viscosity higher with the oil cooled somewhat.

When these cars where sold new I thought there was only single viscosity diesel oil. As oil temperature increased viscosity dropped. Todays multi grade oil chemically changes viscosity to compensate with heat.

I can assure you though at say two fifty degrees straight 40 oil will have more viscosity than a 15-40 multi grade oil. The saying is that multigrades provide equivelant protection to straight oils. They do not state their oils maintain simular viscosity though.

At least this led me to suggest a test for the excess oil consumption. You live in Florida so it should be possible. Try running straight 40 or 50 grade oil. If consumption drops signifigantly it is rings. If not then the chance of a head gasket failure probability increases. You are going through a lot of oil.

At 500 k the piston lands could be so worn that the oil rings are pumping oil. I am still having some difficulty with the excellent compression numbers you got.

Are you sure the trunk badge has not been switched? This sounds more like a 3.5 litre engine.

LOL, yup just the ol' 2.4L four-banger chattering away underhood. And this has only 215K miles on it, my W116 is the 500K+ miler.

We'll do new compression check this weekend and will see if any oil sprays from the open glow plug ports. If I have my tool back in time we'll also do differential compression as well.

I plan to stop by a few NAPA locations locally over the next two days to see if they've got or can get an inexpensive 50W or 20W50 diesel-rated oil for me to try. While at Walmart today getting more of their SuperTech 15W40 Universal I was really considering using the 80W90 gear oil!

__________________
Joe Black
Get yellow fever at ACME!

Just the MB's: '82 300DT (stick), '81 240D, '80 300SD, '80 300D, '81 240D Manual

I think 20-50 multigrade is too simular to 15-40 and may just result in more confusion. You really want straight 40 or 50. Since you already stuffed a viscosity additive in with no effect is not certain enough. I have heard that this brand can be found sitting at the bottom of the oil pan sometimes.

At 215K and you believe the odometer is right. Unless something really odd has happened with this engine usually they are still very good.

I now understand the compression numbers you are getting. A possible head gasket failure is now moving upward. The 40 or 50 oil will tell the story.

I never used oil as a test but on the few cars that consumed oil excessivly in my possession switching to straight 40 from 15-30 multigrade halved the oil consumption or a little better. These were cars with known cylinder issues.

Another thing I neglected to ask. You are an experienced mercedes diesel owner. What does the blowby look like from this engine. Excessive or within the normal range. How does it handle the loose oil cap test?

when you do the compression test and the readings are low
put a little oil in the cylinder (tablespoon maybe) and see if you get a significant increase in the reading . If so then you have a ring problem. Your rings could be stuck from WVO usage.
My gut says your rings may be ok as you are not complaining of a bad startup when cold.

You are ingesting the oil from somewhere and a failed vacuum pump would be my first choice.

I'd be careful about putting a tablespoon of oil in your combustion chamber. A teaspoon is more like it. I have calculated the volumn of the combustion chamber before and it is like 1.5 CI. If you get that or more in it you may bend a rod with hydrolock.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

You are right..
We usually give several shots of oil from an oil can.
I don't cook so I am not familiar with excactly how much a tablespoon holds but I know a teaspoon is smaller and would be better.

The volume equates to .03 L which is almost exactly 1 oz.

Therefore, two tablespoons would be the limit.

Piston-type, single line. Eliminated earlier.

Got my differential compression tester back today and also picked up some Rotella 40W from local NAPA, they couldn't get any 50W diesel-rated oil. Hopefully tomorrow or Monday I can get the new compression numbers.

I'm definitely selling the car in the next couple weeks. I'm either going to put a 300D on the road or my M1028 CUCV, I just don't have time or $$$ to rebuild or replace this engine. Hopefully all this information will prove useful to the next owner as I'm a full-disclosure kinda guy and the rest of the car is pretty nice, especially since I welded in new steel in the floor!

__________________
Joe Black
Get yellow fever at ACME!

Just the MB's: '82 300DT (stick), '81 240D, '80 300SD, '80 300D, '81 240D Manual

240D manual

Significant "vanishing" oil. No drips under car while sitting nor idling.
Normal oil pressure (3 while driving, 1.5 - 2 while at operating temperature).

I will have to look around, just asking for a place to get going. Car sat for the winter, this wasn't an issue at all before I took her off the road.

__________________
1981 240D 4 speed (for sale - PM FOR CRAIGSLIST AD)
1984 Fiero project EV Drag Race Car

1982 240D first Benz/first Diesel NO LONGER HERE (all parts for SALE!)
1986 Fiero - stripped due to frame rot, ask for information of parts!.
Three 1996 VW Passat TDIs - one is a parts car, please contact for parts!

Year of the two forty may be relavent.Early versions have a vaccum pump that can have a diaphram failure and feed oil into the intake. Those vacuum pumps have two tubes to them. If car was on vegatable oil let us know. Vanishing oil needs a quart in how many miles now and previously to storage estimate.

I see it indeed was on vegatable oil. Wvo products getting by the compression rings forms a sticky substance in the oil ring lands. Sitting unused for a decent amount of time this sticky residue turns to a solid glue.

I would cease burning vegatable oil. Add two containers of miracle mystery oil to the base oil. Incidentally change the base oil if you have not been changing it fairly frequently as the base oil can polymerize from the byproduct as well.

Add miracle mystery oil to the fuel tank as well. Drive the car for a thousand miles and see if oil consumption is dropping. If not the pistons should be removed and the rings extracted and the glue cleaned out. The syrupy residue when sitting sets into a very hard effective glue. It may be too late to chemically get it out but worth a try. It is a solid indication that car was not combusting all the wvo it was fed. There are some other possibilities but they are far less likely.