300D Synth Oil

Last autumn, I switched to Amsoil synthetic. There were a number of posts here relating to the switch. However, now after three months, my 300D has started a minor leak in the forepart of the engine, and uses
about a quart of oil every 500 miles or so.
Two questions for the group:
1. Will the engine eventually "adjust" to the synthetic oil, and if not, then;
2. Is it adviseable to revert back to dino oil? I have put about 1,200 miles on the synthetic so far.
All advice will be appreciated.
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This is what my local Indy mechanic had to say about the use of synthetic oils in older engines.
Great for the internals, as far as increased lubricity, reduced friction, and reduced dry starts. But...and here is a big But if that older engine has any weak seals or gaskets the Synthetic oil is going to find its way through them a lot easier, and more regularly than a good quality dino oil that is designed for older engines. The trade off is oil leaks, and oil usage. At the cost of Synthetics those are very expensive oil leaks. And No, the engine will not adjust to the new oil, it will just continue to leak. In fact it will probably get worse.

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Well, the benefits cited were, of course, the reason for my decision to switch, but I know you're right, that the problem of leaking will not resolve itself, and that in all likelihood the only smart move is to revert to petroleum oil.
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Chevron Delo 400 SAE 15W-40 (CI - 4Plus) works fine in my 300SD.
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On Jan 10, 6:04 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote:

Well, that's what I've used for years in my diesel M-Bs and I guess I should have stuck with it, as I never had a problem with any of them.
What are your thoughts on changing back after running the synthetic?
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No problem changing back to regular oil. See if you find any visible oil leak and correct it if possible.
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I'll do that. I am very disappointed with the switch.
The oil leak is definitely at the front of the engine, as evidenced by garage floor pooling. I should have no problem finding it. Of course, it did not leak at all before.
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wrote:

I'll do that. I am very disappointed with the switch.
The oil leak is definitely at the front of the engine, as evidenced by garage floor pooling. I should have no problem finding it. Of course, it did not leak at all before.
I hope I'm wrong but I believe once the synth oil starts going past the seals the regular oil will do the same. If it were me I'd revert to the previous oil used, and if that doesn't help, replace the seal, then think seriously about staying with regular oil. Sounds like your car is fairly high mileage, I would expect other seals to be close behind the one already leaking.
I wouldn't call a quart every 500 miles "minor".
Good luck Alan
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Sounds like it's the front crankshaft seal that's leaking. I had that problem on my 1980 300SD years ago and I don't recall it being very expensive to fix. Had it done at a local shop. I believe they have some kind of repair kit seal that makes the job relatively easy. Might have been a couple hundred bucks, but I don't remember it being a major hosing. :)
And it's been fine now for 50K miles and many years. I think this is a fairly common problem.
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Yes, same happend to me in my 300E. I switched back to dino oil without any adverse effects in the long run. My engine stopped leaking again after the switch..... why should there be any adverse effects from swithing back anyway??? the syn and dino oils simply affect the seals differently. I started using a oil 'meant' for older engines and it seems to decrease oil usage between changes.
cheers, guenter

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On Jan 11, 10:55 am, snipped-for-privacy@sciborg.uwaterloo.ca (Guenter Scholz) wrote:

I know that, in the abstract, there should be no adverse effect, but I proceed with caution and ask a lot of question here, because it wouldn't be the first time that I have taken a decision and then found out later that there was some overlooked issue. But I agree that there should be no problem, and do intend to revert back to Delo 400 tomorrow.
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snipped-for-privacy@mac.com wrote:

I guess I'm an exception. I switched my '92 300D to Mobil 1 synth and I lose about a quart every 2500 miles which I consider perfectly acceptable for a car with 226,000 miles.
JD
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I bought my 1982 300 TDT from the original owner (via an agent) in 1993. It had 144,000 miles on it, and I was able to check the maintenance records at the local dealership where the car had been faithfully serviced. The engine was running great, and did so for another 200,000 miles or so. I decided to switch to synthetic oil, and tried Amsoil. Then later I switched to Mobile One, but not a product designed for diesel engines.
It may just have been a coincidence, but the engine started to blow oil out the seals and the amount of blowby increased greatly. I ended up having the engine remanufactured last summer at Metric Motors in Canoga Park, CA. I had used Delo 400 from when I bought the car until I switched to synthetic at about 350,000 miles. I used it for about 15,000 miles (3 oil changes) and the engine went to hell over that time after remaining stable for 200,000 miles with regular changes of Delo at about every 2,000 miles. It was using a quart of oil in maybe 2,500 miles, so I usually never had to add oil.
After running synthetic for 15,000 miles, the engine was leaking a quart of oil every 500 miles. In the case of my engine, it did not help to change back to Delo, the leakage and blowby continued.
The EGR valve also stuck open at about 390,000 miles, making the engine impossible to start. I didn't get that diagnosed until after I had the remanufactured engine in. I don't think that related to the blowby though or the synthetic oil. I suspect that the EGR valve stuck because of the reduced lubriicty of the new ultra low sulfur diesel. I got 396,000 miles on the original engine.
At any rate, I am delighted with the remanufactured engine from Metric. The head on my engine was cracked in 6 places, so I needed a rebuild anyway. The car runs like new now.
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