Synthetic oil will cause some cars to leak and dino oil will stop them?

Group,
A few months ago I posted a question "will an oil leak that started because I put synthetic oil in my motor stop if I go back to dino oil?"
The answers I got were not conclusive but some good thoughts from different people were given, I thank them as always. Here is now my answer to the question based on what my experiences have been. Leaks my start if you use synthetic oil and will stop when you go back to dino oil.
I have a 1981 300sd that is at 118K. It did not leak befor except for an occasional small spot on the floor. I put 5W50 synthetic in to the motor and a few days later I had spots of oil all over the floor. I found the front and back motor seals leaking, the pan gasket oily around the perimeter and dripping, one oil cooler connection with small drip dangling driping always. Might have tightened it but did not. The floor had to be cleaned every week.
3K later I did an oil change using Delvac 10W50 dino oil. The oil leaks have stoped after a couple of weeks of driving. The small spot on the floor that I used to see seems to still be there and it comes from my oil cooler connection. Maybe I should tighten it now LOL.
My conclusion is that synthetic oil will cause leaks in some cars. This my have to do with how the seals and gaskets were designed in 1981, or just the mileage. One speculation is that the seals of this car have only seen dino oil. Dino oil swells some tings and synthetic dose not swell them, so for 115K mile my seals have run swollen against the crank and have worn to the proper friction to still seal thins ok while using dino oil. When I used synthetic oil the seals retracted and leaked. When I used dino oil the swelled back up. Same principle applies to the old pan gasket. Note, I also put 5W50 synthetic into my 560sl at 96K and after 3K it has no leaks.
Thanks Bruce Buchanan
najurb
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Nice follow up.
Thanks.
Miro
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Bruce Buchanan wrote:

AFAIK there is no such mineral oil. Delvac 1300 is the only mineral multiviscosity consumer oil diesel range they produce and it is only available in 10w/30 and 15w/40 viscosities. The 15w/40 meets the highest duty spec for long drain heavy duty engine oil, meeting API CH4 and CI4, MB228.3, ACEA E4 and E5, and, of course, Global DHD-1. All other Mobil mineral oils seem to be monograde 1600 series. Certainly I have never seen a mineral oil with a viscosity range as narrow [and I use 'narrow' advisedly] as a 10w/50 and it is a new one on me, if indeed it exists.
Huw
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Nope! It dose not exist. I just looked, you are right and I was wrong. I put 15W40 went into the car. The point of my information though was not about viscosity, but about mineral oil VS. Synthetic oil.
Thanks, Bruce Buchanan

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Bruce Buchanan wrote:

API CH4 specifies the seal performance characteristics of the oil. Since both the synthetic and mineral Mobil oil meet or exceed API CH4 then both will meet expectations. It is possible and likely that leaks you have experienced are caused by the synthetic having a very light cold viscosity. Maybe.
Certainly I use and have used a wide variety of engine oils, both mineral and synthetic, from various blenders and refiners and I have never been able to distinguish them from leaks. Some seals do leak worse when cold, such as rocker cover gaskets.
Huw
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The age of the car wasn't mentioned as I recall. In any event, it is possible that the car is old enough to have seals in it that are not up to withstanding the additive package that is in the synth. oil and it has attacked the seals. As a former seal design release engineer, I was specing seals made out of Viton as the oils we were going to put into our product would have degraded the seals. Dave HD

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On Sun, 16 May 2004 01:17:16 -0400, "Dave HD" wrote:

This is really scary stuff... you mean that you could kill your oil seals with kindness? I thought whilst reading through this thread that the problem was more likely to be the difference in the cold viscocities of the oil (maybe exaserbated by the existing wear on the seal) causing a pathway for the thin oil to seep through. Switching back to the thicker oil would give the appearance of curing the problem - whereas in reality it would just have altered the symptoms.
Please tell us more about which types of lubricant attacks which age of seal - I am sure I am not the only lurker in the group would hate to kill our Mercs with kindness.
300Essie
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I personally haven't had the problem yet... I switched at 200K miles... from all dino to all synthetic. Car ran alot better and my problems disappeared.
The scary stories you hear is mostly American cars what have high loose tolerance and loose bearings... and they did a engine flush and then switched to synthetic or even stay with dino and the engine seized.
German cars like MB has very tight tolerance that is unlike the american cars... so something like this occuring on MB would be extremely rare and if it did, then the previous owners never took care of the car.
If you still are scared then stick with semi-synthetic oil.
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I have never been able to discern the slightest difference in an engine running characteristics when changed to a synthetic of near equivalent viscosity to previous mineral oil. Long term resistance to total shear breakdown of the viscosity of an oil fill during a heavy duty cycle, yes, a long drain mineral or a synthetic oil provide significant gain.
Huw
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Same viscosity... I am not so sure about this... I pretty much switched from 10W40 or 20W50 to 10W30 synthetics... which is pretty big difference.
My next step is going to 0W40 as all new MB uses and starting to become available from Mobil 1 in general stores... such as Wal Mart.
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Have you evaluated the effects of the additive packages of the oils and their effects on the seal materials??
I suspect that you have seals that were spec'd to withstand the synth oil and or the oil you are using doesn't have anything antagonistic to the seals in it... DaveHD

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Dave HD wrote:

I run engines, mostly diesel, that have been built in a range from 1972 to 2004. The older engines, which have rope seals, have run on a variety of oils over the ages and now runs on additive intensive long drain mineral oil meeting MB228.3. of 15w40 or 10w/30 viscosity. This is far removed from the oil advised at the time of purchase in '72. I also use a fair amount of fully synthetic Super Universal 10w40 [75w/80] oil in both engines and transmissions which have oil cooled brakes and multiple clutch packs. This oil is also used in some older engines with no problem. I assume that this synthetic oil is also very additive intensive with anti-squawk agents and high detergency.
I have no seal leak issues.
Huw
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That's good. I also handled a lot of warranty issues on the ML's transfer cases that were leakers. Just count your blessings that you haven't had a problem, yet... Dave HD

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Dave HD wrote:

I had an ML and it didn't leak. I doubt if any such leak could be attributed to synthetic oil on the ML, which incidentally requires the exclusive use of synthetic oil in its engines used in the USA but not elsewhere.
My vehicles range from new last month to '72. An '84 engine has done a moderate 280,000 miles with no leaks from seals though it has never run on synthetic. I do in fact avoid the use of synthetic oil unless its use is called for. In general I prefer to use a mineral long-drain oil for normal duty cycles. Cost effectivness is the main consideration, not any fear of leakage. I do buy and use both conventional and synthetic oil in fair quantity. Even my synthetic oil is bought in 205litre drums, so I am not entirely without experience in its use ;-)
Huw
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Uhuuumm, not true. The programs that I have worked on have included Ford, Mercedes and GM. There is no longer a difference (generally speaking) in manufacturers. We all engineer to the same specs (DIN, ANSI, FMVSS, etc) and there aren't that many suppliers of seals (or lubricants) in the world. We have moved to a global economy where parts for cars come from everywhere on earth. Korea, Japan, China, US, etc.
The effects that the oils have on seals vary from car to car and manufacturer to manufacturer. That's why it's generally best to follow what's written in the Owner's Manual. The information there is generated from the engineering design of the car. You risk damaging the vehicle when you stray away and try to do "backyard engineering" on your vehicle. I personally put hundreds of hours of testing into the products that I work on.
DaveHD

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Frank Mallory has been using Mobil 1 in his 70's 108 cars fro the day Mobil 1 was introduced. This stuff about seals is nonsene.

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Sorry Honorable Mr Sexton, but the leaky seals are real !!!!!! Just ask my engine seals.
mcbrue resealedly under the bridge in the trailer down by the river
96 S420
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Sample of one. You probably had blowby and the pressure is pushing the oil out past othereise good seals. Lots and lots of poeple use Mobil 1 or bette rin cars much older than yours with no problems whatsoever.
If you have an problem synthetic will make it worse but if your engine is in good shape - no problem at all.
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Who is Frank Mallory?
Top of the Google search is a chemistry professor at Bryn Mawr.
DAS
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http://vrx.net/frank.jpg
Frank had had every cool Mercedes since the 50s and for a while published "The Mercedes Collector" a tremendous technical publication for guys that collect old MBs. This was more or less killed off by the toad Frank Barrett, the vendor that effectively controls the MBCA. Frank ran a BBS for this stuff in the pre interent age then was probably the most helpful guy on the net once it attained ubiquity. His healt is not the best these days and as he says the grim reape is knocking at his door whihc is very very sad; the man is an utter genetleman and one of the most knowledgabel guys around when it comes to 50's and 60's cars.
Google frank at mbz dot org.
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