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rickjordan 12-10-2000 07:02 PM

I have had my 300SD for 2 1/2 months now, and I am trying to get a feel for how much oil she uses. I did an oil change first thing when I bought her, that was about 2k miles ago. At about 650 miles after the oil change I needed to add a half quart. Then about 800 miles later I added another 1/2 quart. I have noticed that when the eng. is running first thing the exhaust (at idle) is tinted blue. However after she has warmed up the blue smoke appears to go away. So I am figuring it's the valve seals that are leaking when she's cold and sealing up when hot. There is however, no puff of smoke when she is started first thing. Which is the usual sign of bad valve seals in a gasoline eng., but I don't if diesels are different in this regard. So is this oil usage seem normal, and nothing to worry about considering the 225K miles on the eng. I am using Castrol GTX 20W-50 per the recommendation of the MB/Porsche/BMW ind. shop that I bought the car from. They use this oil, change it every 3K and she'll run forever.

240Joe 12-10-2000 08:05 PM

Oil consumption

I certainly wouldn't worry about using 1 quart in 1400 miles or so. I personally wouldn't attempt any repair on my own vehicle if using this amount of oil was the only problem.

On gas engines, consuming oil has the problem of fouling the plugs, if the consumption is too much. This creates a real problem, so you have to resolve the oil burning problem. On diesels, that's not a problem.

I would say to check the oil frequently, use an oil with the diesel rating, change it every 5000 or so, and move on down the road.

You can buy an awful lot of oil for the cost of even the most basic repair.

All of the above,of course, is only my opinion. I know this subject can be rather controversial.


rickjordan 12-11-2000 09:27 AM

240Joe, On the subje of diesel rated oil. When my tech. recommended Castrol 20W-50, I went to Castrol's web site to look up if it was diesel rated. Well fro this particular weight, it has no "CH" or "CG" rating but some of their lighter weight oils do. Should I switch and run the chance of having a higher oil usage? Normally such a thick oil would cause cold morning starts, a problem. Since I am using the block heater, she starts rightup even when it's 22 degs. outside.

240Joe 12-11-2000 12:51 PM

Oil for diesels?

I personally would use the diesel rated oils. You can do more research but when I looked into this several years ago, most people indicated that oils specifically rated for diesel are the only way to go. This is what all the big trucks use, and since those companies have a lot riding on picking the correct oil, I would say that someone has done their homework for them. I'm not a chemical, or automotive engineer, but the reason for using diesel oil seems to have something to do with the particles that diesel oil gets contaiminated with. Diesel oils are formulated to handle this whereas the others are not.

I can get Shell Rotella T at Walmart for a fair price, so I go with it. I buy it when I make the normal toothpaste, laundry soap know.

But, as they say, your mileage may vary.


rickjordan 12-11-2000 01:00 PM

This Shell Rotella, how much does it cost at Walmart? There is a Walmart that is 2 towns over from me that I can go to. I actually never heard of Rotella, then again this is my first time looking for diesel grade motor oil. Also, what weight are you using and do you think the weight I am using is too thick? Keep in mind with this thick stuff I am averaging 26-28 mpg in combination driving. Also is this Rotella a synthetic oil? When I bought the car, I asked if I should run synthetic in it. My tech. said he wouldn't recmommend synthetic because it would be a "shock" to the eng. after 20 years of reg. oil. He said, without hesitation to use Castrol 20W-50 every 3K. Any thoughts on this?

[Edited by rickjordan on 12-11-2000 at 01:23 PM]

LarryBible 12-11-2000 02:28 PM

The "diesel rated oil" you speak of is actually correctly called "universal" grade. There is no difference in the "thickness", the difference is the additive formula.

There are many oils that carry a C (compression ignited) rating, but are not specifically for diesel engines. The universal grade has additives that basically have more detergents which can deal with soot dispersal, something that is not an issue with a gasoline engine.

The most common universal grades are Shell Rotella T, Mobil Delvac and Chevron Delo 400. The most common weight is 15W40 which covers virtually any climate.

A new universal grade, and the only synthetic I know of is: Mobil Delvac One. If I were going to use a synthetic in a diesel, this is the only one I would consider for the purpose.

Shell Rotella and Chevron Delo are available at Wal-mart and go for about $5.50 per gallon. These are readily available at Truck Stops on the Interstates and also your local oil suppliers. If you check in your area, you will probably find a few businesses that sell farm fuel, oil and other products to the service stations and such. You can buy them there by the case, pay the tax and save just a little. The main advantage is that these oils which are not so common at the auto supply store, are commonly used for farm or construction equipment use, and available there.

I have run all my diesels on Chevron Delo 400 with great success. I also use it in all my gas engines from my lawn mower, to my four wheel drive, to my wifes 4Runner. The added detergents keep gas engine crankcases clean enough to eat out of.

Good luck,

patsy 12-11-2000 08:41 PM

Hi Rick,

Here is my opinion. I know someone who bought a '79 300SD new. They always used Castrol and still have the car. I use Castrol, although I was tempted to try the diesel oil at my local auto parts store. In winter below freezing, I use 10W40.

Diesels smoke when they are cold, and it is perfectly natural. What isn't natural is when people back up when they are behind you at a drive through restaurant. That happened to me. I had two problems:

A. My turbocharger seal was worn, and since they are oil cooled, a bad seal will cause the turbo to burn that leaky oil. I replaced my turbo and it made a big difference.

B. I had worn valve stem seals, and $10.00 and an afternoon sitting on the radiator was all it took to solve that problem of smoking at idle. Changing those seals is remarkably simple.

smoke would pour out of the tailpipe when I accelerated hard, and I was no longer able to drive anywhere without complete guilt and humiliation. If it gets that bad I would worry about. Until then, I think your oil usage sounds very normal. You found a nice 300SD I'd say.

be459 12-12-2000 03:00 AM

Patsy or Bill

How do I know if a turbo seal is bad? Would the oil drip from the turbo? Black Smoke from the tail pipe all the time or sometimes?


[Edited by be459 on 12-12-2000 at 03:04 AM]

patsy 12-12-2000 12:50 PM

I cannot explain the exact symptoms, because the leak is usually inside the turbo. The oil goes straight out of the exhaust. I had my leaky turbo diagnosed by the dealer, but I replaced it myself. I believe blow-by will fill the large turbo hose with oil, which will drip out, the turbo oil cooler lines have gaskets that will leak. The return line is especially suspect, because it is "held" on by a couple of o-rings. I know my oil return line leaks a lot. I had two problems with similar symptoms. So diagnosing my problem was a little tricky. I did the turbo first, and under heavy acceleration, my smoke problem subsided. Then I did my valve stem seals, and my heavy smoke problem at idle subsided. That's all I can say. Hopefully a tech will give a little input on diagnosing a leaky turbo.

rickjordan 12-12-2000 04:07 PM

I guess my oil usage isn't really something to be concerned with. All my car knowledge and experience has been on gas engines. As everyone knows constant blue smoke is generally a sign of bad rings, so naturally I was concerned. With my car, even when I really get on it, I don't get a cloud of smoke. My folks were up for Thanksgiving and while they were here, I had my father follow me in his '85 300D, to see if I had any smoke. He said he didn't see anything that was noticeable. I guess I lucked out in getting a car with a healthy eng. I bought the car for $1600, that included a new Interstate battery and new exhaust flex pipe.

be459 12-12-2000 10:18 PM

Bill and Patsy

Thank you very much for the reply.


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